if the mechanical shock of the reset bar is tripping the relay, then you'll want to look for wear on the armature plate and the roller lifter arm. Also look for dried grease that may be preventing the armature plate from latching the relay.

if it looks worn, you can swap the pieces with another trip relay that would be less annoying if it trips and see if the problem moves ... then you'd know for sure it's time to source some replacement pieces.

a less common problem is crud on the coil top/armature plate that is causing the plate to stick to coil top ... at least enough for the relay to not reset reliably. However, it sounds like your problem is the relay is tripping when it was already latched/reset, so it's not that (assuming you do howard's test to verify it's not electrical).

you covered the screw ends with tape so the lift arm doesn't touch them?

the only way that could matter electrically is if the entire reset bank frame was electrically connected to something (maybe) and the tubes going thru the switch stack were too short, missing or damaged and allowing a blade to touch the screw threads.

if you left off fiber spacers, the tubes would be too long and you wouldn't be able to snug down the stack and clamp the blades in place.

a more common problem would be the stack is twisted a little and a blade is touching the metal of the lift arm either next to the nylon roller or the entire arm.

it does look like the screw top is getting bashed when the coil activates - you'll see a dimple in the lift arm. The screws are pretty soft, so you can probably cut off the ends in place if you have some strong cutters that fit. Any deformation at the end will fix itself when you remove the screw.

since the screws are threaded into the unit frame, if the frame was energized the screws would be too regardless of the roller arm hitting them ... so ignore that comment.

a question is whether the long screws is factory or not.

if the factory did it, I'd guess they would act as a limiter to the upward travel at the end(s) of the reset bar. The manuals don't say anything, so next monday I'll look in a few wms games at the pacific pinball museum and see.

it's still uncertain if the problem is electrical or mechanical. Howard's suggestion to unsolder the wire from the coil is best, but edednedy suggestion to "block" the coil disconnect switch would work with a caveat ... I'd stick paper around the switch blade that is connected to the coil lug so it can't possibly touch a blade above or below it.

when the reset bank coil fires, the force is hugely more than you can exert by hand and the switch blades and roller arms will have some momentum.

I dunno where in the stack the blade going to the coil is, but if a surrounding blade can get flung into it, the coil could energize and your fix would be to check for missing fish paper or adjust blades so it doesn't happen.

knowing for sure if the problem is mechanical or electrical is really step 1 now.

I was thinking the problem is electro-mechanical.

if the roller arm plate is slamming into the bottom of the screws, that shock is transferring to the switch stack and possibly knocking the switch blades up enough to contact an adjacent blade it normally couldn't touch.

whether that's possible depends where in the stack the blade with the wire going to the coil is, and what wires are attached to blades above/below it (if any).

pictures from the oxo at the pacific pinball museum. It's hard to see how the issue could be electrical - the black wire on the top switch blade (bottom blade in pics) is going to the the 3-in-line trip coil.

unless an insulating tube is missing from the stack, the only way it looks like it could be electrical is a short onto or energizing the grey wire - or the coil lug with the black wire is touching/arcing to something.

oxo_3_in_line_trop_relay (resized).jpgoxo_trip_bank (resized).jpg