It is so unfortunate that we have to put up with this nonsense. IMO the scammers have progressively gotten worse. You have to vet your buyer and your seller.
I have found it is good to have two references from either the buyer or the seller. If you can't communicate with the past transactions then roll the dice! You make the decision! At this point, I lean more towards online dealers. Yes, it is a little more but it is more secure. I was a victim on the receiving end of a PP scam and lost my privileges. The buyer told the official that the unit he received from me was not working. Turned out it was his way of auditioning gear at my expense.