Hey, you have be there to run the machine, but there is an upgrade in the skill tree just after vendingmachine upgrade, that costs only 30 coins to keep it running. Hope you give it try and check it out.
Do you mean that during the second hunt, without going back to the Pachinko Shop, the machine stops processing when you return to the Pachinko Shop?
can you message me on discord
as I am not able to replicate this situation in my device.
Discord link