[hypoxia]

Heat happens when a connection fails for whatever reason. It can be corrosion, loss of tension of the connector or a variety of other reasons. It's one of the reasons simply reseating a connector cures so many problems. Any discoloration on a connector is a warning of heat and a poor electrical connection. It's also why I try to use name brand parts instead of chineesium.

It's good you found it, hopefully that cures your problem.