Couple things to do. Measure DC voltage at the bottom of R114 on the power driver board. This is the +5V test point. If it's low, then adjust the voltage up using the potentiometer at R115.
There is a connector that goes from the top of the power driver board up to the bottom of the CPU board. It sits right above a voltage regulator and the heat can cause the pins to tarnish. Try reseating the connector at both ends first. If it helps for a few weeks, then probably best to replace the headers and connectors.
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