I have different look board.. Did check it fast, seems nothing has burned. I dont get why whould board short on frame.
Eh look at how these things are assembled.
I can only imagine the vibration going through that control pannel.
Heck even any static generated can cause problems.
Sounds like the pot has a internal issue if it works but goes to full before you reach full? < thats how I read your description.
I have same problem with pots on my guitar. Sometimes I get dead zones on my pots. Especially if I dont use them much.
Over the years I have replaced with higher end pots and have less issues.
I would start with a new pot.
Check and fix any poor connections, make sure you have a good ground. Not a bad Idea to use a wrist ground strap when messing with the board.
Relocate and maybe add protective sheathing to potential wear/rub area of any wires.
Why your Outlet breaker tripped and not the machine fuse?
Im going to guess there was a quick jump in amps drawing to the motor directly?
Do you have sensitive ground fault protection breakers?
Its a good time to make sure your breaker is snug and wires to receptacle are tight.
We had to move the power strip on the work bench as the grinder vibrated the entire Bench enough the connections would come loose in the junction box.