S21 "System UI Not Responding" and complete screen failure

[AmyK19]

A few days ago, the screen on my Galaxy S21 randomly flashed with lines like a broken TV and went black. It started working after about 15 minutes, but kept randomly going black for 15-30 minutes at a time. Eventually I got an actual error, “System UI not responding.” Since yesterday, my phone has basically become a brick. It is still on and working because my alarms went off this morning, but the screen does not work at all. Occasionally I can get it to buzz as if it’s failing to unlock.

Things I’ve tried so far:

-Turning off and back on

-Holding power button for 30 seconds

-Holding power button and volume up

-Holding power button and volume down

-Updating all apps and uninstalling 2 apps I had recently installed

-Clearing Chrome cache

-Clearing up memory

-Factory reset and restore (which worked for about a day)

I’m at a loss at this point. Is my phone toast? Is there anything else I can try?

[TechZilla]

It sounds as if you have a loose connection or dry solder joint, also can you notice any bulging in the back of your phone? Maybe the battery has slowly expanded? Just some thoughts, without your screen working at all it's virtually impossible to know what is wrong if it is a software problem.

[MarkS21]

I have a new S21 ultra. Worked great until I noticed an update available. After loading and reboot of the update, the UI 6.1 welcome screen came on.  The touch screen would not respond to any input.  Using the side buttons, I came to the on/off reset screen. Still no touch input accepted.  My cell provider got to a screen where we were able to do a factory reset, but nothing has changed.  I've seen since last year this update has been corrupting cell phones but see no solutions.  They just keep releasing it to earlier phones.