Quoted from clodpole:
New boards installed today... mostly positive results.
Issues: Lower left kicker does nothing, both drop target sets have trouble resetting during play but work at end-of-ball (sounds very much like your situation), and the upper left rollover doesn't register. Otherwise, everything works and scores every time.
Thanks for the update!
I just installed a Rottendog MPU327-4 to rule out the original MPU as a contributing factor to the unreliable scoring on the Flash I am working on. It does not make any difference, nearly every target continues to score intermittently during game play but scores 100% if I trigger them with my finger. Inspected head to PF molex connector and the pins all look great along with the MPU 0.156" connectors. Adjusted every switch to a much tighter gap (1/16") and the scoring is improved, but still not perfect. All switches have been cleaned / polished with Flitz and then cleaned again with IPA. Gold looks great, can see my reflection in the contacts.
A few more things I learned:
* Adding 0.047 uF capacitors across the DT outer pad pairs enables the DTs to score 100% but I see phantom scoring during target reset with the original MPU.
* Those same targets fail to reliably score with the Rottendog MPU327-4 - so adding capacitors will not help games with that MPU.
* I tried 0.01 uF capacitors to see if that would still work with the original MPU and eliminate the phantom scoring during target reset and those don't work with the original MPU.
I am not sure what to do next other than start replacing the diodes. Am thinking of moving to the 1N4148s which are much faster than the IN4001s from the factory. I'll report back if I solve this but running out of things to do next! Thanks.