Published mp4 videos from Storyline are playing chunky, stuttering

Needing help.

I've used Storyline to edit an mp4 video published by my department in a different program.

But the published mp4 video from Storyline never works. No matter what quality settings I've picked, the video always plays chunky, stops and starts. I've tried publishing to the local drive instead of our network drive and it's still chunky. I've uploaded the video to our MS Streams site and it plays chunky in there too.