Yea, it's working well in my server, but i found your problem, NPC 1 is working well, you can't buy the items if you don't have the required item. But in npc 2 you can buy all items even you don't have the required item.
In the npc 2 :
Find all :
$@Dbuy_id
$@Dbuy_co
Replace all with:
$@Dbuy_id2
$@Dbuy_co2
i already replace but same problem can you send me a new script?