Hi 2Smoke
Some thinks that you must check and can cause the PGM to overheat and finally burn are these below :

Power valves cables not well lubricate or cable's wires in bad condition with no smooth movement.
Power valves cables wrong adjustment with too much tension,they need 0.5mm free play.It's better more freeplay than less.
Valves on the cylinder are not clean and they have carbon on them with the result of not smooth movement.

Check out these issues as any of them overheat and damage the PGM.