Hi mate,
Sorry to hear that the game isn't responding well to being recorded!
I've installed Action! on my machine and the game runs at 60fps. What are the specifications of your PC? I assume that other games you have recorded run fine?
Also, if you haven't already, could you give the SDL2 version of the game a try? You can download it from the itch.io website (My Purchases > Loot Rascals > Download > lootrascals-windows-sdl2test.zip). Give it a go and let me know if that makes a difference :)
Cheers,
Max