Losing Left Hand Screen

I've lost the left hand screen on two separate Full Boar 4 now, both while running V3.3.1

The first one was fixed while unplugging and plugging up the screen in different orders, this was after doing a complete install a couple of times. The second was fixed by moving the screen to the third output inside the console as the full install and replugging didn't work

It seems like it's more "software" based than a hardware fault though as everything comes back eventually for no reason.

Any ideas please on the cause and the repair?

Thank you

Mark