yeah... a 9.6v NiMH even on a well tuned AEG
WILL melt the contacts
The reason is melted the trigger and nothing else is because the trigger is your point of highest resistance in the electrical system. And resistance = heat. Holding the trigger down for really long bursts at that voltage would cause that kind of damage for sure.
Here's a pic I took of my buddy's FULLY upgraded M4. prometheus gears, shimmed properly, magnum motor, 350fps, 9.6v 4200mah NiMH batt. Shot around 1200rpm. This was after about 8000 rounds, always short bursts.
And Amos MELTED his triggerblock on his RS Type 97B by using a 9.6v 5000mah NiMH batt lol
Solution : MOSFET switch or triggermaster!