Fraps is very demanding software, but also has very annoying way it's coded. Unlike other capture software such as Dxtory, OBS, Bandicam, ShadowPlay, the Fraps works differently it doesn't have a flexible framerate. Instead it works on the idea of "framerate multiplier checkpoints". It creates these "checkpoints" depending on what is target framerate and will record only at the highest possible checkpoint, if it can't keep up then it will jump down to the previous checkpoint.
So to put it in example:
If your Fraps target framerate is 30 fps, then these checkpoints will be created: 30 fps, 60 fps, 90 fps, 120 fps, 150 fps, etc. If your in-game framerate is 80 fps then Fraps will lock it to 60 fps because that's the highest checkpoint it can reach. If for some reason your framerate will drop even to 58 fps then Fraps will lock it to even earlier checkpoint which is 30 fps until you will regain stable 60 fps performance.
These "checkpoints" depend on what is your target framerate. If your target is 60 fps then your checkpoints are going to be 60 fps, 120 fps, 180 fps, etc. And anything lower than 60 fps will be creating dropped frames. This "multiplier" coding is the reason why I abandoned Fraps and switched to
Dxtory.