In this Update I fixed the recipient inventory where a player was able to take the head out and can't open the sellable item info.

As addition I added a new command:
/shop tradinghistory <player>
Where an admin can see the last 20 trades from a player.
As well as, after a player has sold or bought 6 times the same time, a warning appeares in the console and admin chat (this can be disabled with the options command).

Have Fun!