[Hellfighter]

try Steve away first.

inside the game folder there be another folder call "cache" go inside it delete all the files in it, then exit out of it, try to play the game.
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sound like some thing gone bad, should only see "game over when you finish all the levels of the SP-Mission at the very end it would say that?

i think the game gone bad, save maps and any ????.sav files then unstill it, after delete the game folder totally. restart the PC , back to desktop re-instill the game back in and update it.