TrueNAS Core 13 - Cannot add 2nd SSD to boot pool (mirror)

I just upgraded from 12.0-U8.1 to 13.0-RELEASE, and needed to replace one of my boot pool mirrored drives (as it is old). I DETACHED the old drive (nvd0), shut down the machine, replaced the drive with a new one, and rebooted. When I go to the boot pool and select ATTACH on the remaining disk (nvd1), and then select the new member disk (nvd0), check the "Use all disk space" option, and click Submit, I receive the following errors:

In the GUI:

Attach Device

Error: [EFAULT] concurrent.futures.process.RemoteTraceback: """ Traceback (most recent call last): File "/usr/local/lib/python3.9/site-packages/middlewared/plugins/zfs.py", line 212, in extend i['target'].attach(newvdev) File "libzfs.pyx", line 392, in libzfs.ZFS.exit_ File "/usr/local/lib/python3.9/site-packages/middlewared/plugins/zfs.py", line 212, in extend i['target'].attach(newvdev) File "libzfs.pyx", line 2092, in libzfs.ZFSVdev.attach libzfs.ZFSException: can only attach to mirrors and top-level disks During handling of the above exception, another exception occurred: Traceback (most recent call last): File "/usr/local/lib/python3.9/concurrent/futures/process.py", line 243, in _process_worker r = call_item.fn(*call_item.args, **call_item.kwargs) File "/usr/local/lib/python3.9/site-packages/middlewared/worker.py", line 111, in main_worker res = MIDDLEWARE._run(*call_args) File "/usr/local/lib/python3.9/site-packages/middlewared/worker.py", line 45, in _run return self._call(name, serviceobj, methodobj, args, job=job) File "/usr/local/lib/python3.9/site-packages/middlewared/worker.py", line 39, in _call return methodobj(*params) File "/usr/local/lib/python3.9/site-packages/middlewared/worker.py", line 39, in _call return methodobj(*params) File "/usr/local/lib/python3.9/site-packages/middlewared/schema.py", line 979, in nf return f(*args, **kwargs) File "/usr/local/lib/python3.9/site-packages/middlewared/plugins/zfs.py", line 215, in extend raise CallError(str(e), e.code) middlewared.service_exception.CallError: [EZFS_BADTARGET] can only attach to mirrors and top-level disks """ The above exception was the direct cause of the following exception: Traceback (most recent call last): File "/usr/local/lib/python3.9/site-packages/middlewared/job.py", line 355, in run await self.future File "/usr/local/lib/python3.9/site-packages/middlewared/job.py", line 386, in _run_body rv = await self.middleware._call_worker(self.method_name, *self.args, job={'id': self.id}) File "/usr/local/lib/python3.9/site-packages/middlewared/main.py", line 1276, in _call_worker return await self.run_in_proc(main_worker, name, args, job) File "/usr/local/lib/python3.9/site-packages/middlewared/main.py", line 1192, in run_in_proc return await self.run_in_executor(self._procpool, method, *args, **kwargs) File "/usr/local/lib/python3.9/site-packages/middlewared/main.py", line 1166, in run_in_executor return await loop.run_in_executor(pool, functools.partial(method, *args, **kwargs)) middlewared.service_exception.CallError: [EZFS_BADTARGET] can only attach to mirrors and top-level disks

On the display attached to the NAS:

GEOM_ELI: Devicemirror/swap0.eli destroyed.
GEOM_MIRROR: Device swap0: provider destroyed.
GEOM_MIRROR: Device swap0 destroyed.
Error: one or more plugin init callbacks failed.