since I love being wrong, I'll toss out another possibility that explains all the symptoms, but wants to add one that hopefully wasn't noticed...CU cam 5B is stuck closed.

if that's the case, as soon as the EB trip relays tripped the EB step up coil powered and stayed powered, creating a steady high current drain on the transformer. Note the wipers haven't moved yet since they rotate when the coil unpowers.

when you closed the coin switch, other high power solenoids like the timer cams index and the mixer latch need to power, but you've starved them of current so as nick said the 50V power drooped and the anti-cheat let go.

if you do need a coil, the newer part number is BC-25-925...but your resistance isn't crazy low.

for the spurious pay problem that needs a lot of balls in holes, the most likely thing is a switch gap too small on a search relay. Could also be wiper fingers misaligned or worn down on the search disc so one or more fingers is bridging rivets.

the wipers on the inner couple of rivet rings will bridge rivets in the same ring normally, but as you go further out it shouldn't happen.

you may need to wait for it to happen then go around to the back and manually reset the replay counter unit (assuming there's no valid payouts). Watch the search index unit to see if it's powering or starting to power.

the theory is that you are getting enough search relay switches closed at the same time to power the search index coil. That releases the replay cams and you get a credit or two, but when the search index grabs the ratchet to stop the wipers, the wipers are no longer on winning rivets, so the power goes away.

the search index coil should only power when you have a win that needs paying.

another thing you can do when it happens is carefully stick a business card between the 120V contacts on the tilt trip relay switch L2. That'll shut off the motors. Then slowly turn the search wipers with your hand and see if you can get the search index coil to power ... if you do, see which search relays are powering and work out from the chart on manual pages 162-163 which shouldn't be. Look at the wiper contacts while slightly turning them back and forth. You are trying to see which finger is causing the issue.

doing this you may be able to get the search index to power when it normally wouldn't due to the rotation speed of the wipers, so also spin the wipers back/forth around the trouble spot more quickly and see if the search index coil powers.

in other words, by spinning the wipers very slowly you can probably find tiny spots that cause 3+ adjacent search relays to power, but at normal operating speed the wipers sweep over those spots too quickly for the search relay or search index coils to energize.