The coin mech in the cab I assume is set to accept Japanese 100 Yen coins. I don't have any of those coins but I do a few neat Sega and Konami tokens.
Unfortunately there is no way to remedy this without hacking the bejesus out of that metal assembly. They're also a difficult replacement part to track down so I decide against that - my cool Sega and Konami tokens are a no go. I decide on 20 cent Euro coins instead. A bit more fiddling and all is well. Coin mech adjusted without any hackery!