Poor video quality when screen sharing video

I am trying to run a webinar in which I share my screen and play some pre recorded content. The issue I am having is that when the video is played, the content is blurry and illegible. However, when paused it comes into focus only to then go blurry again a couple fo seconds after resuming. I believe I have done everything I can but wondered if anyone has any possible solutions before I call it quits.

Cheers