This sounds like a faulty control board, most likely there is a crack on the PCB and when pressing the button your bridging the hairline crack.
If there were other sensors causing the fault you would see this in the LCD display.
I would start by removing the control panel and inspect the PCB under a magnifying glass, and see if any tracks are damaged and if any components require re-soldering.
If this is uneventful, the next step is to look at the wiring harness, and power regulator, but the fact the machine comes on if you hold makes me think its the PCB.
Let me know how you get on.
I havent heard back from you in the last day or sp, and just wanted to check if you still require assistance, I would appreciate it if you could rate the service received.