Quoted from megaladon:
Interesting enough though when the magnet holds the ball it somehow deactivates the upper flipper and drop targets and mother hole On that switch string. It doesn’t look like it’s blowing any fuses it just somehow makes them stop working?
You have red "prototype" IO boards? Replace the middle playfield IO board with a newer design one and this issue *should* go away.
I say "should" because the issue haunted us in debugging it, and we believe it's caused by poor USB comms (collapsing due to electromagnetic interference), and the way in which the circuit overload protection circuits interact with the IO control design they chose. HWP hacked/disabled one set of the overload protection in the newer run IO boards, keeping the main protection circuit, and it seems to have helped this particular scenario, but actually doesn't 100% fix the root cause of poor USB IO and interference. I actually have oscilloscope screen captures of the upper right flipper coil getting "locked on" because of the way the USB comm collapses and doesn't receive it's command to switch coil to hold. I've been meaning to do a write up on our findings for some time.
The other thing that has been said 1000 times here is USB cable quality. Get high quality USB cables with the ferrite cores, and shorter the better. Run them away from noisy lines, meaning, keep them away from coils and other sources of EMI.
IMHO, the real fix assuming hardware is unchangeable, would be game code and an IO board firmware update that changed the USB commands around and did coil hold timing on the IO board, rather than in game code, so the board will know when to switch from fire to hold by itself even if USB comms drop, that way not reliant on the USB comms to stay 100% reliable during such timed command. The way it is now, if USB comms drop mid event, it is over taxing the coil drivers causing the protection circuit to save the day (and stop the coil from working until power cycle), but falling back to the main protection circuit isn't actually better either...which I'll save for another day when I can dig up the o'scope pics.