Agreed.However, https://www.umc-uk.co.uk/instruction-manuals/Sharp/5111K suggests that source change selection the [OK] button is the {Vol +} one on the TV... See page 13
Try that button?
I'm sorry, I know it sounds condescending, but can i ask you to get to the menu, press "Channel Down", until First Time Installation" is highlighted, then press "Volume Up" and see what happens?Yep i did try both standby and every other single one seperately just to check i wasnt missing something lol and still no joy
It's just to satisfy my curiosity and if it doesn't work, there's something else going on with your set!