Believe for example Telus has a limited 14 day return window on in-store phone purchases, 30 days from online. Could be from people just deciding they don't like it and out of that return window. I don't believe the ads that state they "bought 2 to see which one they liked".Serious question. All these people on Facebook Marketplace, how do most of them they get the phones they are selling? Second question....has anyone done business with PDA Plaza? Good experience? What's their warranty really worth?
Given issues with some devices I'd only buy something I can personally check in person (also opening the box to make sure its not full of potatoes), and no shipping.
If in doubt ask for IMEI and do a check https://swappa.com/imei
And check both the one on the box matches the one in the box.