Whenever I encounter a matchmaking error, I'm popped "back into" the gym with all the boulders and smaller rocks duplicated. Probably because the gym doesn't fully unload when the match is set up. It also made structures that I had flick on have the flick particles around them but weren't flicked

This has happened for me when I was flying / being moved by a structure, but also when I was just sitting still by the matchmaker