Mana flask loosing charges

I noticed that my mana flask is loosing charges even if I don't use it. Maybe I am missing something? It has chance to gain charge on kill mod, but it seems like it looses charges on kill instead.

What am I doing wrong?
I am playing Invoker monk not Pathfinder concotion.
I have ingenuity belt. Only changes I made before it all started to occur, was unallocating the nod that gives 20 chance flask to not consume charges.

Tried to allocate it back, still loosing charges. I entered map with full charges, killed two or three packs of random mobs and lost 10 charges without using flask.