Gorgon + soul vortex

[PvK]

I see spell effects get abbreviated if I am using a video card with not very much video memory, and am on a map which has lots of stuff in the background - like a view of a mountainous landscape with trees. Pressing 1 to limit background detail helps.

[Quitschi]

Observed it again ...
At the start, right after casting it it worked pretty well, but later on it stopped.
Is the anything that can stop soul vortex, or does it stop at certain opportunities? (no living targets in range,..?)