Well you found the 1 on 1 section.   The main think to check is if the unit is stepping up and down freely by activating the coil manually.   Ifbits ok then check the alignment of the units wipers when it in the reset position.  One coil will step it forward one will either step it back or reset it straight back to the start.

   Let me know once it's stepping freely manually advance the stepper a few clicks then try starting the game and see if it resets if it doesn't pulse the reset coil the problem is further in