Thanks, this was spot on and exactly what was happening. Nice catch!Came here to say this as well; the engine he uses for the game is this obscure fossil called Clickteam Fusion (fun fact: same engine as FNAF) that either can't (or is not coded properly to by Eluku to) handle dynamic refresh rates and just picks the lowest refresh rate your computer reports back to it as the maximum available, and runs with it. This also breaks the game almost entirely as logic, animations and momvement speed run every frame.
So if you have any kind of adaptive sync, not just G-Sync, it will shit its pants.
If on Nvidia, you can disable G-Sync for windowed applications or create a profile for the game (keep in mind new versions will require a new profile) and set Monitor Technology to Fixed Refresh and it will start working again.
If on AMD almost the same thing applies, either disable FreeSync entirely or add a "custom graphics" setting for the game (with the same mention as above)