Most coin-op machines have a free play switch or credit button inside them so it is likely to have one. Alternatively, take wires off the coin mech and add a push button yourself to rack up credits.
If the machine freezes when the door is closed, there is probably some kind of cut-off switch that 'pauses the game' to preserve your credits or just power, a bit like the light switch inside your fridge. Try to find this switch inside the door frame and remove it.