YouTube screen problem on Safari

When I go to YouTube on a new window, everything is fine. I select a video, hit full screen, video plays, & everything is all good. When I revert video back to normal size, that's where the problems arise.

One, the entire page is shifted to the left.

Two, and more annoyingly, any videos selected at this point, for some reason, no longer fit in the video screen. All of the screen control button on the bottom right, including the button for full-screen mode, are no longer fit on the video screen.

Refreshing the page doesn't fix the problem. The only way to fix it is to close the window and reopen YouTube in a new window. This issue does not happen when I use Firefox or Chrome. Let me know if there is a way to fix the issue.