Samba previous versions variably broken in RC1

I've recently upgraded from 11.3-U4.1 to 12.0 RC1 and unfortunately the samba previous versions function seems to have been broken again.

1. The ignore_empty_snapshot VFS module setting is completely ignored.
2. Running samba with debug logging I can see a message (presumably from `shadow_copy_zfs_get_shadow_copy_zfs_data` that 0 snapshots were retrieved for a share.
3. Following on from above with the snapshot cache disabled if I repeat the previous versions lists I can probably 50/50 get a snapshot list to return and the above debug message states that it returned X amount of snapshots. (race condition somewhere?)
4. I've also seen warning log messages that the snapshot path is outside of the current share with seemingly an attempted access to another volumes snapshots. Not going anything concrete on this other than we've seen it several times but haven't managed to narrow it down.

To my knowledge this was all working well with 11.3-U4.1 and has done since some VFS fixes were applied around U1-2.

Not sure how we're doing debugs these days but I can get one no problem.