Even though I thought that one big problem was enough, it seems that that was not the end of it. I do not know why, but SUDDENLY every video I export gets an XMP writing error and, unlike in the past when that didn't affect anything else, the video is corrupted in the last "10%" of itself. It does not end.
I really do not have the slightest Idea of why this is happening. I'm running Premiere 14.3.2 (since the later ones have completely destroyed performance, somehow), latest Nvidia Drivers with a 2080S and an AMD Ryzen 9 3950X.