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 Apple M2 Max, 96 GB of RAM
AC27 US (5003) on Mac OS Ventura 13.6.2
Started on AC4.0 in 91/92/93; full-time user since AC8.1 in 2004