PA would not chargeback a payment that has already been made to you. Furthermore, A refund sent via Paypal cannot be charged back.
Now, what I have had happen before is an order on PA was delivered successfully, and then 1-2 days later PA said the transaction was on hold. They began asking me for a lot of information, I sent regular screenshots, they said they were invalid. Basically, because the payment PA received ended up bouncing on them, they were trying hard not to pay me.
You need to be careful with them, because their profit margins are quite low. If they start losing money on your orders, they will take extra measures to gain that money back.

