Mask syncing.

LR Classic August 2022, Windows 10.

When I try to sync a mask to a series of selected photos, the masks are usually orrectly synced after a short wait. However, if I try to sync a mask to a single selected photo, the mask does not end up in the correct place on the subject and I have to manually drag it.  Any suggestions? Also, how do I access the Update all masks option? Maybe that would work?