[Solved] Only Update button and every asset is marked with plus symbol

After starting Unity and waiting until "checking for changes" was done, every asset had the plus symbol next to it as if I just created it and the collab showed the yellow download arrow as if my collab partner had uploaded (which isn't the case). The collab history even shows that the last upload was actually by me. I also can't publish the changes, there is only a Update button and when I click it, Unity starts downloading the whole project (~17 GB). As the collab download speed is rather slow, I'd rather not have to redownload the whole project for no reason.
I didn't make any changes while Unity wasn't running.
I had very few unpublished changes.
I did close Unity via taskmanager the last time it was running (though in that session I haven't made any changes). Might this be the reason for this? Is there a way to make collab understand that I already have all the assets, "checking for changes" doesn't figure it out.

 

Still the same problem. I only had to download 1.2 GB now however. Everything is back to normal now at least.