This stepper on my El Dorado often lights two match numbers at the end of a game. If I actuate it by hand, I can never recreate this, as it always steps through properly and lights one number at a time, but it must be slightly mis-aligned or half-stepping or something. Has anyone seen this before? Does anyone have any recommendations for what to look at?

I disassembled and cleaned this stepper last year.

Thanks, folks!