Are you certain that the finger on the lever makes good, sold contact with the little "rivet-head" contact. See leftmost picture, where the contact is visible to the right of the lever? And does the pin of the lever make good contact where it pivots?
Check wires from shoes to make sure they have good contact all the way. You're dealing with old stuff, and soldered joints could be failing.
Use eyes and ears. If the headlight doesn't flash, problem is not the shoes. If the e-unit buzz interrupts, and light doesn't flash, problem is in connections between slideshoes & coil, INCLUSIVE. coil.
