Skarner ULT

Sometimes when I use the ULT of Skarner, the animation for the ULT's beginning starts for him, however, the enemy champion is not crystallized, stunned, dragged, or has any of the symptoms that would be inflicted by the ULT. I've noticed this most often when Someone has a Zilean's ULT on them, and today on a Trydamere. He had no banshee's veil, or anything else of equivalency. Perhaps it could also be due to the champion moving simultaneously. This does not happen all the time, even in the same game. However, this happens around half the time I use it, whether it be in the Summoner's Rift, or not.