Hello. Got this board here. No signs of corrosion anywhere. No liquid damage. It works for some time, then dies. If I let it cool down for a couple of hours it works again for some time and dies again. No crash report is generated when it turns on again. Last week I tossed it into ultrassonic cleaner and the board worked well for 3 or 4 days and died again. I'm lost, don't know where to look. Any hints?