You have to think how the hopper works.
It does not have any sensors in the hopper to detect tokens.
All it knows is. That as it turns. It's waiting for a signal from the opto coupler. If it doesn't get a signal. After say 5 seconds. It will assume the hopper is empty and give an error.

That why we asked. When it payout. Can you see the machine counting the tokens it's paid, or does the display stay the same.