Edits disappear

Lightroom Classic-Version: 15.0.1  on Mac OS 26

I wanted to edit photos in LRC for the first time since August and noticed that photos that had already been edited lost all their edits after a “double-click.” The thumbnail image in grid mode is initially correct, but after double-clicking, the image and thumbnail image revert to their original state.

This started with version 14.5.x (unfortunately, I didn't note the version number) and is still present in the current 15.0.1.
Restoring the catalog file “Lightroom - xxx.lrcat-data” from the backup had no effect.

Fortunately (and strangely enough), the change log for each photo is still available, so I can restore the edits, but doing this for each photo is impossible.
Even stranger is the top entry in the history all photos: “Export - Hard Drive (12/02/24 07:56:48),” but I can't remember having done this!

Other potentially useful facts:
* I have several catalogs, but I haven't changed catalogs recently
* I still have the problem that I can't always switch to the next image in development view (neither with the key nor with the mouse). Therefore, I uninstalled and reinstalled LRC. Unfortunately, I can no longer say whether this was in December 2024.
* I updated my subscription form in October.
* I also disabled GPU usage, but unfortunately this did not help.

I am more than grateful for any advice!