As of the most recent update (finished today at 1pm gmt I think) vortex now occasionally just stops dead in its tracks even though I continue to hold down the right mouse button for it to move along its path.
I tested a bit and it has nothing to do with the mouse cursor being over some ui elements like your skills or minimap and there was nothing in the way that could have blocked my path either, I tested by moving the same path multiple times.