It might be worth the time (~10 minutes) to pull out that board so you can really examine every switch on that bank. It’s such a nuisance to work on from a remove, especially when it’s in the rear of the cabinet where it’s deepest, like it is on Dimension. Also, bank switches behave differently in the service position because of the different gravity. Once you get it out of the cabinet, you can really see how the switches make/break when tripped, if there are any tabs touching things they shouldn’t, solder splashes, etc.

PBR has stock of those plates with the insulating lifter. They are needed to ensure good make/break operation on those lower switches labelled “armature” on the schematic. They also insulate the bank from the line voltage on the LB and AB armature switches. Without the insulation, those switches will touch the assembly and juice it up with 120 volts. I got a good zap from an electrified bank while adjusting something on my Mini Pool.