I'm having a really strange problem, and I can't figure out what's causing it. I just started using source control for my ~2-year-old game project, and I pushed all the game files to the repository. Then, today, I did some cleanup and deleted a bunch of extraneous objects and sprites I wasn't using anymore, then pushed those changes to the repository. Now, suddenly, my game runs at double speed in fullscreen mode. It's set at 60 fps, and when it's in fullscreen it runs at 120. This doesn't affect the real fps, and the debug graph does show the observed fps doubling. I can confirm that the deletion of those objects didn't cause this, since I pulled back the older version and the problem persisted. Even if the pull screwed up somehow, I went back through all the objects I deleted and none of them had any code that would have caused this problem. The weirdest part is that the game is sped up as well as the frame rate. I'm not using delta_time, but I'm using a system where all my step and alarm values get multiplied by a value to automatically correct for a different hard-coded frame rate value, so the game should still be running at the correct speed. I'm not sure why it isn't. I'm on IDE 126.96.36.1998 and runtime 188.8.131.52. I've tried toggling vertical sync, using an older runtime, and restarting the IDE and my computer, and nothing solved it. I feel like the source control somehow had something to do with this since I've never had this issue before, but I don't understand how it could have messed things up, since rolling back didn't fix it and I verified all the objects I deleted had nothing to do with it. Anyone have an idea of what's going on? EDIT: Okay... so, I made a backup of the entire game project right before I did any source control stuff, and I tried importing that backup and running it. The frame rate is still doubled in fullscreen mode on that project! So at this point I can only assume that something outside of GMS is screwing around with things.