Those are replacement boards not originals. Only one opto is required for your machine. I would advise caution with these boards - I don't know if this applies to your boards or not BUT they very likely do not use the correct opto interrupters as they have not been available for many years. Standard optos just don't cut it.

We redesigned the circuitry to allow standard optos to be used on the replacement boards we make. Several other manufacturers don't and I am very dubious about them and have done many tests to prove my point. Those boards could very well be the cause of your weak flippers and might actually cause damage to the fliptronics board.

I would swap in some boards from another game (as long as they are originals) to test.

Also, I would repair the faulty coil, simply unwind a turn and reconnect the wire to the terminal - this is a VERY common issue and also a very common way of repairing the coil. No need to chuck out a perfectly good coil.

Be careful with this. I have mentioned why already