Vaal spark Soul count lost

Idk if i'm missing something on several last patch notes or this is a bug, but here it is:
My vaal spark will automatically lost all soul after it's fully charged. This happen about 10 extra kill after full charge. No use, nothing happen except i have to charge soul again. It's pretty frustrating since i always save it for tight situations and bosses.

Sorry for my poor english, poor explaination.

do you have tempest shield running?(maybe herald of thunder?)
If you cast tempest shield in your hideout it resets the soul count any time you re enter the same area(for example if you port to town then back)

try casting auras in the zones you are going to rather than in the hideout