Mirrors do not work

The same thing happened to all my vehicles as well. I haven't touched the mirrors in literally ages (the script, model nor the texture and settings in the content tool). I think in the spring it was working everywhere, now it doesn't. I checked if there were some non-backward compatible changes in the mirrors (like when at sounds the looping was added years earlier), but nope, in my vehicles every value seems fine.

One thing I noted: the mirrors look like the coordinates were faulty (it is only rendered in z direction, therefore it only consist of lines, which actually represent the map around the vehicle).