Hey evab3aver,
Was the video created in Photo Booth? If so, we recommend restarting the Mac and attempting to play it again. If you continue to experience the issue, test in safe mode. Safe mode helps determine whether the issue is related to software thats loads as the Mac is booting up.
Follow the steps below to boot into safe mode or in this article: Use safe mode on your Mac - Apple Support
If you're using a Mac with Apple silicon
1. Shut down your Mac.
2. Press and hold the power button on your Mac. As you continue to hold the power button, your Mac turns on and loads startup options. When you see Options, release the power button.
3. Select your startup disk. It's named Macintosh HD, unless you changed its name.
4. Press and hold the Shift key, then click the “Continue in Safe Mode” button below your startup disk.
5. Log in to your Mac. You might be asked to log in again.
If you're using an Intel-based Mac
If you're not using a Mac with Apple silicon, you're using an Intel-based Mac.
1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
2. Release the key when you see the login window, then log in to your Mac.
3. You might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right corner of the window. If you can't start up in safe mode, make sure that your Mac isn't using a firmware password.
Depending on the outcome, use the steps in the article above to resolve the issue.
If the video was originally created in Photo Booth, providing more details about how it was created may help you get more answers.
Take care.