Audio suddenly Out-of-Sync, affecting even all autosaves

Hello everyone,

I am writing to you in desperation. This is the strangest thing I have ever encountered working with Premiere and I don't know how to fix it, even describing it is hard.

I finished a project yesterday. I rewatched it one last time, everything was good, saved and was done for the day. Today I wanted to check everything again with a fresh eye. I re-opened the project, started to watch and was hit with an out of sync audio. No problem. There are autosave-files, right? Well, they are all the same. The strange thing is, it only affects roughly the first half of the timeline (so not all clips are out of sync). After then it is (mostly) sync again. Like I said, it is also affecting every autosave.

It is also is NOT timeline specific. I work with two timelines within the project. One for the rough-cut and then one for the final one. In both of those timelines the clips are out of sync. This makes me think that Premiere is "reading" the source audio-files wrong, right? But I literally changed nothing about them. Does anyone have an idea, what could have caused this? I am absolutly clueless and therefore can't even attempt to fix this. I tried it on my Mac (other computer) same issue. All files are stored on an external SSD.

I sunk 30+ hours in this project already and the deadline is right across the horizon. So I am having a small breakdown right now. If anyone has an idea on how to fix this I would be absolutely grateful.