I bet those 2 defective Denon units came from Panurgy, which was where Best Buy sent my AVP-A1HDCI twice.
I have not heard of any defective Refurbished Yamaha or other brands that do not use Panurgy.
PanurgyOEM is an authorized repair service for Denon, Marantz, Panasonic, Canon. So don’t buy any refurbished items from Denon, Panasonic, Canon if they come from Panurgy.
https://www.panurgyoem.com/authorized-service/
Now that Pioneer and Onkyo are part of/associated with D/M, I bet they will now also use Panurgy.