I just played a Hog race on Alpine Rally where the hogs kept respawning over and over, so noone could pass the finishline because there were dozens of hogs in the way. The increasing drawcalls also absolutely killed the framerate and the game wouldn’t load back to the main menu. I was forced to restart.
It’s not a glitch or bug, but rather a form of trolling that players have found in the race gametype. It’s unfortunate, nonetheless. Hopefully 343i can find a way to get rid of it without destroying the gametype (despawning old vehicles would be a good start).