I never heard of that problem before.
I don't know your computer specifications, but somethings that you can do to speed up your computer are:
Do not download things while you are testing or building the game.
For now try not to put too many lights in your games, because that takes a lot of computer power. Just stick with the ambient light.
Run just the necessary programs in the background.
Upgrade to the latest version of FPS Creator.
Maybe depending of your computer specification upgrade your video card drivers or just get a better video card.
Why don't you post your computer specs and we can go from there. Try those things first.
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