Screen going black on iPhone 12

Thanks for the details, Carlover007.

You can try the steps listed here for third party app issues: If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support

If this is still unresolved, contact the app developer for further help: contact the app developer

Best regards.

Hello Carlover007.

Thanks for reaching out to Apple Support Communities. Which app are you using to watch the video? Safari, YouTube , or another app? If you are using Safari, let's the steps here: If Safari displays a blank page or quits on your iPhone, iPad, or iPod touch

Cheers.