1. If you haven't already, try swapping the power adaptor on the warm one, with one of the other XM's.
- if the warming anomaly follows the power adapter (happens on the other XM), then the power adapter may be the fault, as it may be producing a different voltage than specified, (still within the XMs ability to operate, but causing the XM to work harder, and be warmer).
2. Better yet - probe a voltmeter (multimeter, if you have one) on the warm one's power adaptor - see what the voltage reads directly.
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