Update 12.0 to U1 causes Command timeouts and multiple zpools to become unavailable

System is stable running 12.0 base. Shortly after update to U1, received emails notifying of known disk issues related to FAILED SMART self-checks (in process of replacing shortly) such as

New alerts:
* Device: /dev/da13 [SAT], ATA error count increased from 9 to 10.

Current alerts:
* Device: /dev/da3 [SAT], 4 Currently unreadable (pending) sectors.
* Device: /dev/da3 [SAT], 1 Offline uncorrectable sectors.
* Device: /dev/da8 [SAT], FAILED SMART self-check. BACK UP DATA NOW!.
* Device: /dev/da8 [SAT], Failed SMART usage Attribute: 5 Reallocated_Sector_Ct..
* Device: /dev/da0 [SAT], not capable of SMART self-check.
* Device: /dev/da3 [SAT], FAILED SMART self-check. BACK UP DATA NOW!.
* Device: /dev/da3 [SAT], Failed SMART usage Attribute: 5 Reallocated_Sector_Ct..
* Device: /dev/da3 [SAT], Self-Test Log error count increased from 17 to 21.
* Device: /dev/da13 [SAT], ATA error count increased from 9 to 10.

but sometime shortly after (from minutes to just about an hour) I get an updated email notifying of UNAVAIL pool(s).

New alerts:
* Pool Pool-01_2x3TB_Z1 state is UNAVAIL: One or more devices has been removed by the administrator. Sufficient replicas exist for the pool to continue functioning in a degraded state.
The following devices are not healthy:
Disk 13469299449177422213 is REMOVED
Disk 18225843187637751625 is REMOVED

Current alerts:
* Device: /dev/da3 [SAT], 4 Currently unreadable (pending) sectors.
* Device: /dev/da3 [SAT], 1 Offline uncorrectable sectors.
* Device: /dev/da8 [SAT], FAILED SMART self-check. BACK UP DATA NOW!.
* Device: /dev/da8 [SAT], Failed SMART usage Attribute: 5 Reallocated_Sector_Ct..
* Device: /dev/da0 [SAT], not capable of SMART self-check.
* Device: /dev/da3 [SAT], FAILED SMART self-check. BACK UP DATA NOW!.
* Device: /dev/da3 [SAT], Failed SMART usage Attribute: 5 Reallocated_Sector_Ct..
* Device: /dev/da3 [SAT], Self-Test Log error count increased from 17 to 21.
* Device: /dev/da13 [SAT], ATA error count increased from 9 to 10.
* Pool Pool-01_2x3TB_Z1 state is UNAVAIL: One or more devices has been removed by the administrator. Sufficient replicas exist for the pool to continue functioning in a degraded state.
The following devices are not healthy:
Disk 13469299449177422213 is REMOVED
Disk 18225843187637751625 is REMOVED

Checking /var/log/messages is this:

Dec 26 10:12:42 freenas-rms     (da7:mps0:0:16:0): READ(16). CDB: 88 00 00 00 00 01 68 4a e9 60 00 00 00 08 00 00 length 4096 SMID 645 Command timeout on target 16(0x0010) 60000 set, 60.202389277 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 16 for SMID 645
Dec 26 10:12:42 freenas-rms     (da7:mps0:0:16:0): READ(16). CDB: 88 00 00 00 00 01 68 4a e9 60 00 00 00 08 00 00 length 4096 SMID 645 Aborting command 0xfffffe010db2e2b8
Dec 26 10:12:42 freenas-rms     (da7:mps0:0:16:0): WRITE(10). CDB: 2a 00 f5 7a 41 d8 00 04 d0 00 length 630784 SMID 822 Command timeout on target 16(0x0010) 60000 set, 60.211860396 elapsed
Dec 26 10:12:42 freenas-rms     (da8:mps0:0:18:0): READ(10). CDB: 28 00 75 95 a2 88 00 00 80 00 length 65536 SMID 816 Command timeout on target 18(0x000a) 60000 set, 60.211873174 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 18 for SMID 816
Dec 26 10:12:42 freenas-rms     (da8:mps0:0:18:0): READ(10). CDB: 28 00 75 95 a2 88 00 00 80 00 length 65536 SMID 816 Aborting command 0xfffffe010db3c880
Dec 26 10:12:42 freenas-rms     (da8:mps0:0:18:0): READ(10). CDB: 28 00 75 95 a2 08 00 00 80 00 length 65536 SMID 698 Command timeout on target 18(0x000a) 60000 set, 60.340101584 elapsed
Dec 26 10:12:42 freenas-rms     (da8:mps0:0:18:0): READ(10). CDB: 28 00 75 95 a1 88 00 00 80 00 length 65536 SMID 489 Command timeout on target 18(0x000a) 60000 set, 60.398693933 elapsed
Dec 26 10:12:42 freenas-rms     (da4:mps0:0:13:0): READ(10). CDB: 28 00 75 95 a4 88 00 00 80 00 length 65536 SMID 559 Command timeout on target 13(0x000b) 60000 set, 60.414102026 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 13 for SMID 559
Dec 26 10:12:42 freenas-rms     (da4:mps0:0:13:0): READ(10). CDB: 28 00 75 95 a4 88 00 00 80 00 length 65536 SMID 559 Aborting command 0xfffffe010db26f28
Dec 26 10:12:42 freenas-rms     (da3:mps0:0:12:0): READ(10). CDB: 28 00 75 95 a4 90 00 00 80 00 length 65536 SMID 602 Command timeout on target 12(0x000c) 60000 set, 60.536237026 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 12 for SMID 602
Dec 26 10:12:42 freenas-rms     (da3:mps0:0:12:0): READ(10). CDB: 28 00 75 95 a4 90 00 00 80 00 length 65536 SMID 602 Aborting command 0xfffffe010db2a8f0
Dec 26 10:12:42 freenas-rms     (da4:mps0:0:13:0): READ(10). CDB: 28 00 75 95 a4 08 00 00 80 00 length 65536 SMID 697 Command timeout on target 13(0x000b) 60000 set, 60.658369333 elapsed
Dec 26 10:12:42 freenas-rms     (da3:mps0:0:12:0): READ(10). CDB: 28 00 75 95 a4 10 00 00 80 00 length 65536 SMID 859 Command timeout on target 12(0x000c) 60000 set, 60.716850790 elapsed
Dec 26 10:12:42 freenas-rms     (da5:mps0:0:14:0): WRITE(10). CDB: 2a 00 cf 8e 90 a8 00 00 58 00 length 45056 SMID 446 Command timeout on target 14(0x0011) 60000 set, 60.781890314 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 14 for SMID 446
Dec 26 10:12:42 freenas-rms     (da5:mps0:0:14:0): WRITE(10). CDB: 2a 00 cf 8e 90 a8 00 00 58 00 length 45056 SMID 446 Aborting command 0xfffffe010db1d750
Dec 26 10:12:42 freenas-rms     (da14:mps0:0:27:0): WRITE(10). CDB: 2a 00 cf 8e 90 48 00 00 58 00 length 45056 SMID 649 Command timeout on target 27(0x0012) 60000 set, 60.904812950 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 27 for SMID 649
Dec 26 10:12:42 freenas-rms     (da14:mps0:0:27:0): WRITE(10). CDB: 2a 00 cf 8e 90 48 00 00 58 00 length 45056 SMID 649 Aborting command 0xfffffe010db2e818
Dec 26 10:12:42 freenas-rms     (da6:mps0:0:15:0): WRITE(10). CDB: 2a 00 cf 8e 88 60 00 07 e8 00 length 1036288 SMID 583 Command timeout on target 15(0x0013) 60000 set, 60.1029242264 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 15 for SMID 583
Dec 26 10:12:42 freenas-rms     (da6:mps0:0:15:0): WRITE(10). CDB: 2a 00 cf 8e 88 60 00 07 e8 00 length 1036288 SMID 583 Aborting command 0xfffffe010db28f68
Dec 26 10:12:42 freenas-rms     (da4:mps0:0:13:0): READ(10). CDB: 28 00 75 95 a3 88 00 00 80 00 length 65536 SMID 675 Command timeout on target 13(0x000b) 60000 set, 60.1155205855 elapsed
Dec 26 10:12:42 freenas-rms     (da3:mps0:0:12:0): READ(10). CDB: 28 00 75 95 a3 90 00 00 80 00 length 65536 SMID 775 Command timeout on target 12(0x000c) 60000 set, 60.1214052189 elapsed
Dec 26 10:12:42 freenas-rms     (da1:mps0:0:10:0): READ(10). CDB: 28 00 fa ec 41 20 00 00 80 00 length 65536 SMID 767 Command timeout on target 10(0x000e) 60000 set, 60.1244367865 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 10 for SMID 767
Dec 26 10:12:42 freenas-rms     (da1:mps0:0:10:0): READ(10). CDB: 28 00 fa ec 41 20 00 00 80 00 length 65536 SMID 767 Aborting command 0xfffffe010db386a8
Dec 26 10:12:42 freenas-rms     (da2:mps0:0:11:0): READ(10). CDB: 28 00 fa ec 41 20 00 00 80 00 length 65536 SMID 578 Command timeout on target 11(0x000d) 60000 set, 60.1366931409 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 11 for SMID 578
Dec 26 10:12:42 freenas-rms     (da2:mps0:0:11:0): READ(10). CDB: 28 00 fa ec 41 20 00 00 80 00 length 65536 SMID 578 Aborting command 0xfffffe010db288b0
Dec 26 10:12:42 freenas-rms     (da1:mps0:0:10:0): READ(10). CDB: 28 00 fa ec 41 a0 00 00 80 00 length 65536 SMID 801 Command timeout on target 10(0x000e) 60000 set, 60.1496735489 elapsed
Dec 26 10:12:42 freenas-rms     (da2:mps0:0:11:0): READ(10). CDB: 28 00 fa ec 41 a0 00 00 80 00 length 65536 SMID 892 Command timeout on target 11(0x000d) 60000 set, 60.1555541084 elapsed
Dec 26 10:12:42 freenas-rms     (da0:mps0:0:9:0): READ(10). CDB: 28 00 fa ec 43 a0 00 00 80 00 length 65536 SMID 810 Command timeout on target 9(0x000f) 60000 set, 60.1599611643 elapsed
Dec 26 10:12:42 freenas-rms mps0: Sending abort to target 9 for SMID 810
Dec 26 10:12:42 freenas-rms     (da0:mps0:0:9:0): READ(10). CDB: 28 00 fa ec 43 a0 00 00 80 00 length 65536 SMID 810 Aborting command 0xfffffe010db3c070
Dec 26 10:12:42 freenas-rms     (da1:mps0:0:10:0): READ(10). CDB: 28 00 fa ec 42 a0 00 00 80 00 length 65536 SMID 752 Command timeout on target 10(0x000e) 60000 set, 60.1720593886 elapsed
Dec 26 10:12:42 freenas-rms     (da2:mps0:0:11:0): READ(10). CDB: 28 00 fa ec 42 a0 00 00 80 00 length 65536 SMID 808 Command timeout on target 11(0x000d) 60000 set, 60.1779450090 elapsed
Dec 26 10:12:42 freenas-rms     (da0:mps0:0:9:0): READ(10). CDB: 28 00 fa ec 44 a0 00 00 80 00 length 65536 SMID 426 Command timeout on target 9(0x000f) 60000 set, 60.1826374956 elapsed
Dec 26 10:12:42 freenas-rms     (da0:mps0:0:9:0): READ(10). CDB: 28 00 fa ec 44 20 00 00 80 00 length 65536 SMID 700 Command timeout on target 9(0x000f) 60000 set, 60.1884557776 elapsed
Dec 26 10:12:43 freenas-rms     (da0:mps0:0:9:0): WRITE(10). CDB: 2a 00 70 40 27 50 00 00 08 00 length 4096 SMID 916 Command timeout on target 9(0x000f) 60000 set, 60.827126265 elapsed
Dec 26 10:12:43 freenas-rms     (da2:mps0:0:11:0): WRITE(10). CDB: 2a 00 70 40 27 48 00 00 08 00 length 4096 SMID 854 Command timeout on target 11(0x000d) 60000 set, 60.884782873 elapsed
Dec 26 10:12:43 freenas-rms     (da1:mps0:0:10:0): WRITE(10). CDB: 2a 00 70 40 27 48 00 00 08 00 length 4096 SMID 623 Command timeout on target 10(0x000e) 60000 set, 60.943332036 elapsed
Dec 26 10:12:43 freenas-rms     (da8:mps0:0:18:0): WRITE(10). CDB: 2a 00 e5 95 a0 f0 00 00 08 00 length 4096 SMID 528 Command timeout on target 18(0x000a) 60000 set, 60.1001827882 elapsed
Dec 26 10:12:43 freenas-rms     (da4:mps0:0:13:0): WRITE(10). CDB: 2a 00 e5 95 a0 f0 00 00 08 00 length 4096 SMID 420 Command timeout on target 13(0x000b) 60000 set, 60.1060720636 elapsed
Dec 26 10:12:43 freenas-rms     (da3:mps0:0:12:0): WRITE(10). CDB: 2a 00 e5 95 a0 f0 00 00 08 00 length 4096 SMID 883 Command timeout on target 12(0x000c) 60000 set, 60.1119711278 elapsed
Dec 26 10:12:46 freenas-rms     (da6:mps0:0:15:0): WRITE(16). CDB: 8a 00 00 00 00 01 b0 4d 9e d8 00 00 00 28 00 00 length 20480 SMID 929 Command timeout on target 15(0x0013) 60000 set, 60.38550836 elapsed
Dec 26 10:12:46 freenas-rms     (da5:mps0:0:14:0): WRITE(16). CDB: 8a 00 00 00 00 01 b0 4d 9e d8 00 00 00 30 00 00 length 24576 SMID 386 Command timeout on target 14(0x0011) 60000 set, 60.103505142 elapsed
Dec 26 10:12:46 freenas-rms     (da7:mps0:0:16:0): WRITE(16). CDB: 8a 00 00 00 00 01 b0 4d 9e d0 00 00 00 30 00 00 length 24576 SMID 692 Command timeout on target 16(0x0010) 60000 set, 60.169085370 elapsed
Dec 26 10:12:46 freenas-rms     (da14:mps0:0:27:0): WRITE(16). CDB: 8a 00 00 00 00 01 b0 4d 9e d0 00 00 00 30 00 00 length 24576 SMID 786 Command timeout on target 27(0x0012) 60000 set, 60.234615252 elapsed
Dec 26 10:12:48 freenas-rms     (xpt0:mps0:0:16:0): SMID 1 task mgmt 0xfffffe010daf8158 timed out
Dec 26 10:12:48 freenas-rms mps0: Reinitializing controller
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 16
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 18
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 13
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 12
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 14
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 27
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 15
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 10
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 11
Dec 26 10:12:48 freenas-rms mps0: Unfreezing devq for target ID 9
Dec 26 10:12:48 freenas-rms mps0: Firmware: 20.00.07.00, Driver: 21.02.00.00-fbsd
Dec 26 10:12:48 freenas-rms mps0: IOCCapabilities: 1285c<ScsiTaskFull,DiagTrace,SnapBuf,EEDP,TransRetry,EventReplay,HostDisc>
Dec 26 10:12:50 freenas-rms mps0: Error reading device 0xa SATA PASSTHRU; iocstatus= 0x47
Dec 26 10:12:56 freenas-rms mps0[3392]: Last message 'Error reading device' repeated 4 times, suppressed by syslog-ng on freenas-rms.rmscomputersystems.com
Dec 26 10:12:56 freenas-rms (da8:mps0:0:18:0): Invalidating pack
Dec 26 10:12:56 freenas-rms da8 at mps0 bus 0 scbus0 target 18 lun 0
Dec 26 10:12:56 freenas-rms da8: <ATA WDC WD30EZRX-00D 0A80>  s/n WD-WMC1T1274257 detached
Dec 26 10:12:56 freenas-rms GEOM_MIRROR: Device swap2: provider da8p1 disconnected.
Dec 26 10:12:56 freenas-rms da3 at mps0 bus 0 scbus0 target 12 lun 0
Dec 26 10:12:56 freenas-rms da3: <ATA WDC WD30EZRX-00D 0A80>  s/n WD-WMC1T1274257 detached
Dec 26 10:12:56 freenas-rms ses0: da3,pass4,da8 in 'Slot 01', SAS Slot: 1 phys at slot 0
Dec 26 10:12:56 freenas-rms ses0:  phy 0: SATA device
Dec 26 10:12:56 freenas-rms ses0:  phy 0: parent 5003048000b626bf addr 5003048000b6268c
Dec 26 10:12:57 freenas-rms GEOM_MIRROR: Device swap3: provider da3p1 disconnected.
Dec 26 10:12:57 freenas-rms (da3:mps0:0:12:0): Periph destroyed
Dec 26 10:12:57 freenas-rms da3 at mps0 bus 0 scbus0 target 12 lun 0
Dec 26 10:12:57 freenas-rms da3: <ATA WDC WD30EZRX-00D 0A80> Fixed Direct Access SPC-4 SCSI device
Dec 26 10:12:57 freenas-rms da3: Serial Number WD-WMC1T1274257
Dec 26 10:12:57 freenas-rms da3: 600.000MB/s transfers
Dec 26 10:12:57 freenas-rms da3: Command Queueing enabled
Dec 26 10:12:57 freenas-rms da3: 2861588MB (5860533168 512 byte sectors)
Dec 26 10:12:57 freenas-rms da3: quirks=0x8<4K>
Dec 26 10:12:57 freenas-rms (da8:mps0:0:18:0): Periph destroyed
Dec 26 10:13:56 freenas-rms 1 2020-12-26T10:13:56.670542-05:00 freenas-rms.rmscomputersystems.com smartd 7937 - - Device: /dev/da3 [SAT], FAILED SMART self-check. BACK UP DATA NOW!
Dec 26 10:13:56 freenas-rms 1 2020-12-26T10:13:56.993394-05:00 freenas-rms.rmscomputersystems.com smartd 7937 - - Device: /dev/da3 [SAT], Failed SMART usage Attribute: 5 Reallocated_Sector_Ct.
Dec 26 10:13:57 freenas-rms 1 2020-12-26T10:13:57.370463-05:00 freenas-rms.rmscomputersystems.com smartd 7937 - - Device: /dev/da3 [SAT], FAILED SMART self-check. BACK UP DATA NOW!
Dec 26 10:13:57 freenas-rms 1 2020-12-26T10:13:57.855543-05:00 freenas-rms.rmscomputersystems.com smartd 7937 - - Device: /dev/da3 [SAT], Failed SMART usage Attribute: 5 Reallocated_Sector_Ct.

Da3 and da8 are in the same z1 pool (Pool-01_2x3TB_Z1), so I do understand the why the pool is pushed offline, but at issue is that 12.0 base does NOT have this issue, it is the application of 12.0-U1 which has introduced this instability/issue (possibly something within the change to OpenZFS?). I have reverted back to 12.0 base and this issue has disappeared (the da3 and da8 SMART errors continue to be notified, but I do not see any of the command timeouts and pools being pushed offline.)