Lightroom switches randomly between two sets of albums

Hi everyone,

since I started using Lightroom (not classic), I ran into the following issue:

Lightroom opens with one of two different sets of my albums. The first set consists of my very first three albums and exactly 257 images I have imported. The second set consists of all new images and albums I have imported.

On some startups, I see only the first set of albums. Then I close and reopen and after a few tries I see the other set of albums. I never see both at the same time. Which set I see seems completely random. It is about a 70% chance that I see the first set and 30% that I see the second set.

Also when using Lightroom Classic and syncing the online catalog to my harddrive, I can only get the first set of albums.

This seems not to be a syncing issue, as the exact same behaviour can be observed with the web version of lightroom. This means that all images have to be synced to the cloud. A screen recording of the issue: https://www.youtube.com/shorts/WLdZiNUzxkY 

I have never seen anyone else with that problem online. What is this switching behaviour? How can I get all my images at every startup?