Plus 4 here. I've been playing with friends on multiplayer and they all have this issue at some point in the race. I have a controller and this never happens, but I tried using the keyboard to see if this happens to me as well, and within 2-3 minutes it started happening. I tried to notice what's the pattern but I couldn't. I thought it was after crushing on other cars in the race, but as the video from @MattZrh shows, that's not the case. Remapping the keys works for a while until it breaks again for the new keys.
I checked the network stats to see if lost packets are causing this, but i've noticed that this happens even when no packets are lost.
We cannot play anymore because of this... waiting for a fix ASAP.