Ah ha. The board shows it excessive heating. I hesitate to call it 'burnt' as its not a circuit. For the ammeter, the board itself is only a support. If the material is solid, you probably can use it as is. If so, maybe add a fiber washer to add a little more insulation. If the material is really burnt so its crumbling and has no strength, might be able to reinforce it.
Definately excessive heat at the ring connection. Since its only one side - something related to that ring terminal had high resistance. Nut was loose, or the crimp is poor, or wires corroded. The other end of that wire goes into the welded main splice. I'd also check that for signs of heating on that end.