Smooth Playback Issues

Hello everyone!

I am having a problem when I try to play back my video from the HitFilm Express 2 editor. The video will be smooth for a couple of seconds and then be choppy for a bit and even the audio will become choppy then it will be fine for a bit then lagg once more and crash while haveing the audio playback perfectly. I have window 8.1 with an I5-4690k with 8GB of ram and an R9 290 all at stock speeds. Thank You!