Hi okirkpat,
We understand you're having some issues when using full screen mode for video in some apps or sites on your Mac, and we'd like to help.
So the community can offer the most relevant info, we'd like to ask a few questions.
First, since we may not all be familiar with the video content you're playing, can you describe the issue for us? What are you expecting to see? What exactly is occurring?
Which version of macOS do you have installed? How long has this behavior been occurring?
What happens when you try to play the same content in Safari?
If you haven't yet, we also suggest creating a new admin account, and testing to see whether the same behavior occurs there. This can help isolate whether the issue is occurring system wide, or may be specific to a software or settings conflict within your account. Set up users, guests, and groups on Mac
We look forward to hearing back from you!