Check out the patch notes for the v17 Precursor Update here:

B4 changes

MapleStory 2 Rep: 1,605
Posts: 250
in Suggestions and Feedback
I always thought u lose ur b4 key when the gate opens hence gives no incentive for people to scam when buyers pay at chest. After getting scammed for pay at chest I was confused why would someone lose his key and not open the chest, but I realized they lose the key when chest opens. Change it so you lose your key when the gate opens, and system keep track of the player that opens the gate and only that player can open the chest. Making no incentive to scam at chest. Enable more players to enter to prevent buyers not paying, so person refuses to pay kick and find a new buyer. Best system for both parties.