Saw someone asking whether PayPal ever sided with the seller - it did once in my case. I had sold a working laptop to a person who first claimed that I was scamming her since she couldn't find the shipment tracking using the number I gave her (turned out she wasn't even using the correct site), then once the laptop arrived, she said it worked for the first day and then stopped working. I sent proof that the laptop was working, that the customer had already accused me of fraud, that the same customer had confided in me, that she had a lot of telephone bills to pay (she had sent me payment 4 days after the purchase was complete) and that she herself had claimed that the laptop was working when she first received it. PayPal decided in my favour there
How did you prove that it was working? Just by what she said originally? Paypal can and does side with the seller in rare cases, but you need to make sure you're covered with as much evidence as possible. You must always get a tracking number that needs a signature from the recipient that can be checked online. I've always wondered what would happen if a seller claimed he had received something but that it was just an empty box with something to weigh it down etc. How could the sender prove otherwise really? At the end of the day ebay just comes down to blind trust really, but it is so easy to scam people on there, especially when paypal refund money without looking into the case much.
I had taken pictures of the laptop before shipping, with the camera date at the bottom and additionally printscreens from the working laptop itself with the calendar opened. Of course, these can all be faked, but it always helps to have such evidence backing you up.
PayPal is buyer-biased at times, but for example right now I have an ongoing dispute about a laptop I received which isn't working (ironic...). PayPal is reviewing the claim - they asked me to send them a certified note from a third-party qualified technician that the laptop is not working, such as an invoice for repairs, etc. Again, easy to fake, but it's not an automatic payout by PayPal whenever a buyer opens a case.