Just wanna add that this is still happening but in a way that no one has mentioned yet. For me, it seems to happen when they try to ride their bikes inside (not even on campus) and it happens with the Growing Together bike as well. The only time my Sim turns invisible is when they try to ride their bike through a door. They'll get stuck in the door way, then the bike will kinda teleport somewhere random on the lot and it'll go through walls until they get outside, all with the Sim being invisible. I can try to add a video if that's necessary!
