I get people who claim something is faulty, but won't provide photo proof, nor return the item. But demand refunds. I tell them I can't offer you a refund without seeing the fault or having it returned. They threaten Negative feedback and/or a dispute. So I tell them feel free to file a dispute as PayPal will require them to return the item at their own expense. I never hear from them again.

I used to just give in and give refunds and always tried to please the customer regardless of whether they were in the wrong. But I've had so many try it on, that I've given up on it. I seem to cop less aggression when I'm more forthright.