Pretty much the same here, >3 months later, albeit now Rush also has crazy input lags, and/or freezes in terms of registering inputs. Tweaked everything I could at the BIOS, NVidia App, thermals, reducing graphics settings to bare minimums within the game (I have an RTX 3070 with decent cooling, so this shouldn't really be necessary), etc., levels, but to no avail. The game is just incredibly unstable; after almost 2 months of it genuinely being unplayable (no player in Rush being able to control their virtual player and everyone just running in random input-lagged directions), it was fine for a week or more, but now it's back to being unplayable at least in (consistently) Rivals but, (less consistently) generally in any UT mode...
(edit: it's not my internet either, in case someone comes up with that as the reason, I'm on fiber optic cables in a major city in Switzerland...)