If the top left one is working that means there is at least a signal going for it to flip. The coil may be bad but you’d have to test to confirm.

Pull and check it's fuse with a meter, it's on the fliptronics board.

Tests - Switch Edge - push the left flipper button in slowly and see if both optos register on the DMD, for lower and upper.

LTG : )

Not weird at all.

Each flipper button opto board has two optos. One for lower flippers, and one for upper flippers.

Please check this.

LTG : )

Try the flipper test. It should energize the power and hold windings of each flipper separately, so I you can see if it's a coil/driver problem

I'm the case of demo man specifically, the upper flipper isn't staged, since they use the handle buttons as the secondary flipper inputs.

Ok so since both of them are registering properly this points to either a bad coil or bad driving transistor. more likely to be a bad coil.

Sounds like both optos are working. You can check the switch matrix in your manual. The dedicated switches are on the right hand column, that would tell you what the switch by number is.

I know you posted visually no broken connection. Please go over the coil lugs again. The thick wires to them soldered on good ? The diodes soldered on good ? And from the coil itself to the coil lugs, there is a thin wire from the coil to each lug. Dig around them to see if there is a crack or break you can't see.

You could try a different coil, or swap left and right coils, to see if issue moves.

I doubt transistor, then the flipper would lock up on power up.

LTG : )