Yep thats whats happening, too much power for that plug. It is better to direct solder 16g wires to the heater board and us a high amp plug before doing anything else.

There is also what is known as the dual input power mod. The main power plug on the main board isn't rated high enough. It is rated 10 amps on its best day, however 8amps is the max you should run through it continuously. The dual input power mod wires the positive 16g wire directly to a powersupply tap. Then thet 16g ground goes to the plug on the main board. The newer wiring harnesses have only 4 wires on that white connector. I sanded the white connector down to make room for direct soldering the wires to the heater board. The remaining small 4 wires don't need to be rewired, they are low current sensor wires.