Im almost sure you're talking about the ones that sell F to C Grades in Tows, they are a server to client related issue that needs to be fixed. Have been used Blackmarket and never ocurred that. Still if you're starting just use them for now, anyways you can get better gears from quests that needs you to kill Chiefs. You always get disconnected here and there when buying armor/weapon from this merchants but it is what it is. Only use blackmarket when you have the gold to spend, with that said, as for now dont spend your money on it.

Got it thanks!!