Because file your using is A Variable Frame Rate (VFR) file. C:/Users/GameHound/Desktop/Recordings/RobloxPlayerBeta 2018-12-21 18-06-41-97.avi checking VFR: pkt.duration 1
Instead of repeating everything here, there has been another discussion here:
I actually downloaded and installed Fraps. There is very little control over your settings. The software appears to be severely outdated as they can’t even update their copyright dates from years ago. Try using OBS, it’s far superior.