This is one experience. I have some exchanges with paypal and their answers were perfectly accurate and personalized. After many transactions, I have no reason to complain for now. About the case of the OP, I once had 2000€ credited on my bank account for no reason. I knew it was an error and did not touch it. Several days after, the amount was silently debited. No message from the bank. This is not specific to Paypal.