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If he did report legitimate bugs, look into them and fix them if they are serious. If you owe him money offer to send it to him via whatever wallet he wants to use. I think it's 10-30 dollars so nothing big, then click the ignore button and move on.
As a business, it's in your best interest to try and listen to any and all accusations within reason. If there is no scam, explain your case and go on about your day. No need to argue back and forth or submit to any sort of blackmail. As long as you didn't scam, you have no worries. If you offered to pay him whatever money he has coming and deny him the privelege of playing on your platform, then it's on him for not taking payment.
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That's the "issue" here, they can't send the fund because he refused to give a return address. They initially asked for KYC, but after JPR refuses, they waived the KYC requirement and asked him for an address to return his fund. He refused to provide it; because after his fund returned, he's very likely won't be able to play on the platform anymore.