if the contact is shot, you can get new contacts/blades from the pinball parts suppliers or scrounge some used switch blades with good contacts and swap them. A picture of the switches with a tape measure next to them would help. The blade length and the distance between the two stack holes/screws are the important dimensions.
below is what a EM slot book says about the B switch(es). Another possible issue is something wrong with the clock and the timer links are moving too fast. If the first reel is latching too fast, you have a problem.
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The "B" switch is in the open position where it remains but for a segment of the kickoff/wind-down phase. To adjust this switch, set the timer link to its longest stroke by turning the variator counterclockwise until the variator link reaches its shorÂtest length. Hold the clock fan and cycle the reel mechanism. The "B" switch should close and stay closed until it is off the ramp portion of the timer link.
Repeat the above process but with the variator set with the variator link arm reaching its longest length, resulting in the timer link having its shortest stroke. Again the "B" switch should close at kickoff and stay closed as long as it is on the ramp portion of the timer link.