Just got back to the game. Forgot I had Dragonium Z already in my account and it's in one of my pokes in my full PC. I actually scanned the PC for items but I guess my eyes failed me(happens) so I bought it again with 75 PvE coins.
Maybe add a way for us to know the number of a specific z-item that we have(backpack + pc/party mons holding it)? Or give a warning that I already have one when I'm trying to buy? Idk, maybe I'm just used to mega stones not being duplicable so I don't have to worry about something like this for them, I wish it's the same for Z items.