Oh I didn't know that.
Fast forward: I'm testing out if it still happens with fabricloader installed as a seperate instance.
Results: as expected?
So it seems that it is indeed the fabric loaders fault.
Very well, I will look for a way to contact someone who works on (?) fabric.
You can close this thread (I don't really use any forums, I just heard people saying things like this)
Thank you for your help!