MicroX display not showing anything

[Laserjones]

I recently bought a used MicroX. The display worked when I first tested it, even though it was quite dark. Today I turned it on again and found that the display does not display anything. The red light is still there (though weak, not visible in bright daylight), but no text. Otherwise, the device works normally.

I tried the Troubleshooting procedure from the manual (holding down [Exit/Cancel], pressing [Utility], adjusting contrast with the value dial), but it does not change anything (the brightness stays the same).

I also tried a factory reset. The manual says I should hold down [Enter] and [0] while powering on, but there are no such buttons. In another forum I read that it's actually the [Exit/Cancel] and [Menu/OK] buttons (can anyone confirm that?). But this did not change anything either.

Interestingly, when the device has been off for a while and I turn it on again, I can briefly see "Starting system ..." and then the KORG logo, but then nothing again. When I turn it off and immediately on again, this does not appear. So it might be a temperature-related problem?