So now I have around $2K that was held back from this month's App Store payment, it is "balance carried forward" to next month, and from googling it looks like this is likely due to this cycle of refunds occurring, all from this one guy which triggers an investigation by Apple.
Fortunately it now looks like they are paying that balance out on Oct 31, 2024 (which is not a normal payment date), so I assume they investigated, saw what happened and approved the payment.
A week after we disabled subscriptions in Poland, the guy emailed again, in Polish, translated as "Why can't I buy a subscription, please, I promise I won't cancel it again"
sigh, guess it really was one guy...definitely not enabling it again for Poland if the system allows one individual to keep buying and refunding over and over again! Not only did it temporarily kill my app's numbers (they've bounced back again after the refunds stopped) but caused a delayed payment on top of it! All due to one guy in Poland!