either the amp is not built to last(design issue) or the amp grounding is not sufficient or no solid contact to the body causing arching.
Or the amp cannot be bridged to 2ohm load to drive ur sub since its a 4ch...
Or ur speaker mid terminals is touching the metal door panel
Or
Strands of copper cable is touching the +ve and -ve terminal causing it to goto protection mode
Or
Power and ground cable is touching due to poor termination on the amp side......and many other variables..but wont be difficult to find the culprit as ur is a simple setup.
Juz tinkering..

hu wont cause amp to fail..vs wont solve the issue, totally irrelevant. Preferably repair ur hu remote out, try not to use the acc output.

Happy icing