How long is the video? Did you work from a template or not? If so, which one? Did you add audio to the video?
Have you tried to close the project and reopen it on a new page? Can you download the video and play it on your device? Do you see the glitches?
There are a few workarounds you can try:
• Try playing it from another browser, such as Microsoft Edge, Safari or Chrome • Test in incognito or privacy mode • Clearing the cache/cookies from the browser
If the issue persists, can you share a video when you're playing the video?