[CrossKill]

PROBLEM SOLVED
***I asked someone in-game: I had to separate the arena coins packs*****

I get DC imminently after I buy stones
Only after relogin i get the stones I bought but

[vladdidar]

Yes, and put them in slot 1

[Navmesh]

Another hints, do not have more then 4000 Arena coins with you, also all should be in one place (better in 1st slot). And in the end, do not buy with CTRL+Click, just Drag and drop items from NPC to your inventory.