In the 2nd pic it looks to me as though that yellow/red wire has been moved, in order to bypass the diode.. that diode would be doing NOTHING. I would be moving the wire back to the lug the opposite end of the diode (unbanded end) is soldered to, and replacing the diode.

the two lugs the wires are soldered to in that pic are the switch contacts, the 3rd lug is just an anchor point for the diode anode (unbanded end) and the wires, and just 'floats in the breeze' so to speak.

Solder the new diode back in just as the old one is, and move the yellow/red wires to the lug the unbanded end of the diode is soldered to. The original diode must have failed, and someone just said.."oh i'll just bypass it" 

Thanks for that. I've moved the wires over, I'll just have to get a new diode and hopefully it'll work properly.