Since the diagnostics tests are passing, I'm wondering if maybe one of the coin door buttons (advance) is being seen as pressed as that also enters admin mode.
Side info:
Quoted from EvanDickson:I forget what the single digit is for.
the 1 next to the 2503 is the rom release version and the 4 on the credit is the admin mode it is in, 4 being audit/settings range [0, 50]