How about this one we ran into today?
This is a summary on an Adobe group that describes someone else having the same issue we ran into today.
"Longtime After Effects user (20+ yrs), never encounter this issue where it will not save a project. Threw me a major curveball end of the day yesterday because I didn't even realize it wasn't saving either my manual saves (I'm pretty consistent about manually saving every 15-20 minutes) or autosaves... even though the usual prompt window was appearing and telling me it was saving. Did my usual Command-S and Command-Q end of the day and was confused why AE was still open this morning. Shrugged it off, did a bunch of work then realized after a 'Save', then noticed the block in upper left red close button indicating the file was unsaved. Ended up Force Quitting and lost about a combined 3 hrs of work."
This is an identical description of my Senior editor/animator's experience today. He lost 2-3 hours of work. Thanks for taking us backward Adobe.