Part 1: Supermario - If a player goes for the third ! block that has a chance of appearing to summon Luigi, they can get behind the Bowser motivator.
Part 2: Cube - If Hale uses the large laser beam trap at the start of a round, it can kill multiple people at the start with it's reach.
Part 3: Goldfever - Every few rounds, the BHOP minigame will break. Not allowing either Red or Blue team to win.
Part 4: Hot_Desert - If one or two players run into the spinning trap after the car, they might get it to break and spin forever.
Edit: Dlux - If a heavy has GRU while playing Skyfall, they will fall down then start floating back up. It also looks like the "bleed damage" from the gloves isn't working properly like on Ironworks.
Edit 2: On dr_space players can stall infinitely in the choosing room at the end.
Edit 3: On gaytower scouts can hit their baseball at the wall that comes out after the two double jumps and stop it completely.