mount points for datasets "disappear" after replication

Following up on a request for help I posted in the forums:

I have set up a few replication task from a 9.10-U6 to another box which was then upgraded to 11.2-U4. The replication task is still running without errors after the upgrade but something weird is going on with the mount point. Let's take the dataset plexmediaserver_1 as an example:

• It's listed as a dataset:
  root@vault:/ # zfs list|grep plex
  biggertank/jails/plexmediaserver_1 5.99G 26.2T 3.90G /mnt/biggertank/jails/plexmediaserver_1

• It is mounted by zfs:
  root@vault:/mnt/biggertank/jails # zfs mount | grep plex
  biggertank/jails/plexmediaserver_1 /mnt/biggertank/jails/plexmediaserver_1

• mount confirms:
  root@vault:/ # mount|grep plex
  biggertank/jails/plexmediaserver_1 on /mnt/biggertank/jails/plexmediaserver_1 (zfs, local, nfsv4acls)

• However, the mount point does not exist at all:
  root@vault:/ # ls -lad /mnt/biggertank/jails/plexmediaserver_1
  ls: /mnt/biggertank/jails/plexmediaserver_1: No such file or directory

• unmount and mount fixes this, but only until the next replication runs.
  zfs umount biggertank/jails/plexmediaserver_1 && zfs mount biggertank/jails/plexmediaserver_1

My datasets and my pool are not read only, I confirmed this by zfs get all|grep readonly|grep -v off and by running zfs set readonly=off tank followed by a reboot.

This is getting slightly more annoying as it now affects my home dataset (which was previously not affected!), preventing users from logging in as the ssh keys are no longer "visible" on the box.

I am happy to provide more details, almost all of my datasets are now affected. and I can reproduce.

Here's the forum post for reference:

https://www.ixsystems.com/community/threads/empty-or-non-existent-mountpoint-after-zfs-replication.76160/#post-531791