hasn't been reported before, did you toggle the fixture quality option off and on in the settings?

Yes.
I think I understand what happened:
1. I enabled the "fixture quality" mode on computer 1.
2. I built stuff , it had decent quality etc
3. Over the weekend I played Rimworld on another machine, where the "fixture quality" was off - that disabled the quality of course
4. I enabled that option on that new machine
5. It enabled th quality again, but seems the quality on already build staff makes it awful by default
6. I built new stuff and it had proper quiality also after reloading the game

So in short: it seems enabling the "fixture quality" when stuff is already build, will make it "awfull".

i had fixture quality enabled, had no problem. then i build some furniture with setting quality and suddenly all my bathroom items are awfull quality. (At least thats what seems what happened).