Two recurring mistakes i've seen mentioned are:
1) As i said, putting the PS5 horizontal with the disc reader on top (so really, upside down).
2) When vertical, inserting the disc in the wrong direction (with the read-part inwards and the graphic outwards) because of the intuitive assumprion that the lens would be inside the console, where the hardware is, instead of being on the external part.
Also if you pull the USB from the cord to detach them (which you shouldn't do in the first place, but still) when horizontal, some people have had it slip away from the base on to the table/floor.
There are so many things that bug me, like the absurdly complex base, or the USBs being in the middle when vertical, or the power/eject buttons not being contextually placed and almost invisible... i dunno it's one of those things were the more i think about it, the weirder it gets.
To me, it remains the most puzzlingly designed console i've ever seen this side of the NES, but of course yeah, it's relatively minor stuff.
Hopefully they take a good look at what can be done, when the inevitable Pro/Slim comes out.