By skyforbes I just did some testing by switching between mobile app and web.
Gemini seems to prioritize mobile's up-sync: do some stuff on mobile app, immediately refresh the web page on PC, and you will see the new stuff there.
However, when you open the mobile app and the chat you've had in the web interface has not yet been down-synced to your device, then the app's cached (but stale) state gets the priority. The app then immediately up-syncs its 'stale' state as the newest version and overwrites the true latest state (which include your work done in the web). And voila, hours of work gone poof.
IMO this can be easily fixed by forcing the app to do a client-server handshake everytime it's opened, but maybe google thinks that little delay is too much of inconvenience?