Hmm, thats strange. Im assuming you made sure you were recording in 30 or 60fps. If so it could be a problem with rendering the footage or something? what cpu do you have? Another thing is to check your file size, one time i had obs record a 6 minute video and it ended up being like 400gb because of some stupid reason i dont really remember, but if that is the case it will most definetly lag when you try to view the video