My Mrs had to stop selling abroad ( never had a problem with Ireland though). Customers would pay via PayPal, then either say that they hadn't received the goods(that had been signed for ) , or just claim that we'd scammed their PayPal account. PayPal would just refund them no questions asked . Sometimes they'd just go to their bank , and their bank would just snatch the money back from PayPal. Sometimes the scammers would say that they hadn't received the goods , so we'd send replacements , and then they go to PayPal or their bank.
The best advice that PayPal or eBay could give , was