Sounds like a corroded contact somewhere. Some voltage/current can pass but the resistance, at the corroded spot, is to high so the voltage drops very low when any sort of realistic current is drawn. I suggest cleaning up all contacts and checking all crimps to see if they are corroded. If you find a corroded crimp, replace it. That may require replacing a contact pin or possibly a whole connector.and the other (LH) with 3.7.