No changes were made to HAMMER1 that would effect the btree code, so I suspect it is a coincidence.
If the main filesystems look ok it could be that the error resides on one of the snapshots. You can try deleting all the snapshots on the source machine via 'hammer prune-everything <filesystem>' and then see if you still get mirroring errors. If you still get mirroring errors after doing that, your best bet would be to backup the two PFSs in question, then destroy and recreate them and restore. -Matt
