AC19 -- never seen this before, and nothing in Help:
Favorites Palette displays a "Deleted" control light -- not too concerned because Favorites can be Imported from our Template, but curious just-the-same.
Not sure what it means, as the Favorites are still there. Members are still joined to the project in TW with no other issues.
MacBook Pro 2.4 GHz Intel Core i9, 32 GB of RAM
AC25 US (3011) AC24 on Mac OS Catalina 10.15.7