I think I have finally figured it out when it comes to the custom team names not displaying properly in certain events. I thought it was limited to certain event types, but as it turns out, it simply DOESN'T work period in Race Creator, while it always works in Career mode. I am aware that the devs themselves pointed out in the patch notes that they fixed it in only some parts of the game, but still, how hard can it be? So I guess the code is either a mess or the devs just don't care enough.
Even the team radio nonsense with the engineer constantly reminding you that your teammate has crashed in every race (that they claim to have fixed with this patch, but more like the other way around as it was never an issue for me before) seems to only or mostly be happening in Career events and not Race Creator. Add the performance spikes to it (mostly on certain weather settings and with many cars around you) and you have a pretty confusing final patch.
They DID finally fix the two biggest issues though (nemesis system and Photo Mode being useless on keyboard), so at least there's that. But still, it's been a year, it's pretty much the end of support and we are still left with some issues.