How to fix stuttering MP4 export. Desperate at this point!!

I had the recorder and studio set to record and store to an external hard drive. When I export the file to MP4, the playback stutters every few seconds. I have copied the trec and tscproj to the local disk, re-exported and still the same laggy looking playback. I have used Handbrake to try to re-encode but still getting the same exact result. Any creative solutions? It took forever to capture this footage so would be pretty devastating if there is no fix.