ELIXIR STACK in NPC

I have a problem when I put elixirs in a npc... I set these items stack to 50.
Elixirs, but can buy max 5 at once and they will split after u buy them, but its possible to put them in stack of 50! (it also crash the client if I try to buy it via CTRL). Works fine when fusing.

DB and Media parameters correctly set.

Any possible way to fix this?

Thanks in advance

Easy to fix.
The stack size, you have to match them on both tables, the _RefObjItem ([MaxStack] column) and _RefScrapOfPackageItem ([Data] column), also do this client-sided.
According to your "it is stackable to 50, after having purchased them" it's clear that you have only set them properly at _RefObjItem.