not sure how handy you are, but you could take the board out inspect it, check all the diodes, resisters, and if any test bad or cracked, etc. using a soldering iron and repair board. the color bands on the resister tell you what ohm's rating is.
From your comment, it seems most likely that one or more of the solder joints that connects the green terminal block on the right to the PCB is dry, cracked or is somehow otherwise failing. Strain on the PCB connections from the wires pulling on the terminal block is the likely cause.