Stand up board has a chip, I think a TC9164 (9163?). This is the board with the
input jacks on it.

It's been awhile but IIRC this chip runs the LEDs, and is either logic or bus
controlled. I've replaced more than one of them for this kind of problem.

Shouldn't be too too hard to get, I've seen them in other brands, and again
IIRC they cause similar symptoms.

JURB