Very strange sync issue in LrC. Pics disappearing from collections.

I noticed recently that a few collections in my cataloague were empty. It seemed very random.  I located the pics that were supposed to be in those collections in thei folders.  When I tried to re-add them back to their collections, they would add. but then immiedietly disappeat a few seconds later when the sync occured.  All the collections involed are synch'd collections.

I have tried:

Un synching and resyncing the collection

Creating a new collection and synching that

"Rebuilding all synch data"

The problem now seems to be with the pictures themselves that were previously in thee collections... they symply will not stay in a sync'd collection.

Any help would be much appreciated.

-Ben

Mac OS Ventura