Darius W with Vlad pool

I was playing top lane against a Vlad as Darius and I noticed this happening to me 4 different times. It was pretty crappy. When I w and start the animation to hit him and he pools right then, Darius will sit there mid animation and be stuck for at least 2 seconds maybe more. I cant move or anything, but if I e or auto a minion it resets it and I can move again. The first two I was stuck for 2 seconds about but the last two I autod a minion for one and use my e to see if it would work and it did. I hope you at least test it out yourselves and see if you have it too or if there was some circumstance I did not see.