Running game while constructor running causes poly soup

I've been running my game and leaving Constructor running while testing things.

If I do this (this is using TGEA BTW), I get poly soup all over the screen in the game. If I exit Constructor first, then everything is fine.

I'm running in DX Windowed mode on a dual screen monitor configuration. It's not a showstopper, but it would be nice to leave Constructor running while trying things.