Metal deformation in the wheel stopper hole of the score assembly. This causes the machine to hit max score, rather than zero score, on reset.

Spare backbox has this problem even worse.

Scores are wrong on startup, with baseline being 40000. It is possible the spider arm was reinstalled in the wrong position after disassembly for cleaning.

Special hole not sensing or ejecting.

We had this problem once before and it turned out to be score wheel related but now I am not so sure

Score wheel was overwound and would not always increment. After winding to the standard 3 turns the reset is slow and sticky. This wheel also needs to be removed and cleaned.

Step up wheel needs disassembly and lubrication