Oven touchscreen issue

Just bought a Delonghi DEP7410P pyro oven second hand.

Upon connection and turning breaker on, all touch screen controls work, except the power button.

If touchscreen goes to idle (clock showing), no touchscreen controls work.

If I flip the breaker off and on again, then I have access to all controls again, except power button.

If while I still have access to all controls, and I turn on oven as if I was cooking something, and the oven heats up, the power button starts to work.

All controls stay usable even if touch screen goes to sleep, until it cools down. Then it locks up again.

What could be causing this?