Here are a few ideas to minimize risk:
-Do a FaceTime/Google Meet/Zoom call one on one with the seller to walk through the machine.
-Setup the shipping yourself. Ask for an address and photo of their drivers license.
- If they won't do that, tell them to go outside and take a picture of their house to see if it matches the google maps photo.
-Pay the balance of the machine once the pickup is setup and the machine is packed up. (I've done a transaction where I paid the remaining 90% of the machine on a video call when the STI guys were there. Once I sent the PayPal funds, the seller allowed them to put it on the truck).
-Oftentimes, a seller is the second or third owner, and can link to the listing they originally purchased from. this can at least prove some chain of sale with multiple photo sets on the same machine