I posted a bug report for this, but as I probably made the report in horrible hurried garble, I'll repeat it. I was on the level with the 4 spawning trojans in a graveyard. It was the one with the bubbles that follow and explode on you. There's a party button up a hill...and when I approached and stepped on it, I fell through. No major harm done as I was able to walk away with no difference. I could see if it's repeatable, but just a heads-up.