It seems to me to be certain cars. It certainly isn't my imagination.
I even think that it comes down to each track you race on. It's so weird.
The tracks seem to dominate and make a mockery of settings on cars, too. It's frustrating.
They work properly for me as well, this guy had been making these claims all week and (at least in GR3s) I've found no evidence to support what OP is stating.