Found another issue today: If the game "crashes" (i.e., Game Maker pops up an error window), window_frame_host.exe doesn't exit and just sticks around forever.
Also, if I'm in full-screen (via window_frame_set_fullscreen(true)) and I'm not running through the IDE/runner (found in a YYC package build specifically) game maker's error popups show behind the game so I can't see them and I can only close them or exit the game by pressing "enter"