Syndra Bug/Lag

So I was playing Syndra and during the game I was able to ult without issue until this one point. Now, it could be possible that I had packet loss but I felt like I should put this on the forums because it could have been a strange bug interaction with Hecarim ult. Basically what happened was that I threw my combo at hecarim and then ulted immediately after. However, instead of casting R immediately following my combo, I proceed to walk to his position when I cast it and stand still for a brief moment. Then the ult casts ** about one second after I furiously click to run away.** During this time, my ping doesn't fluctuate and my fps remains around 100 so, by my lack of deep internet knowledge, I assume this is a bug. I hope a rioter could clarify if this is actually a bug or maybe it is some underlying problem with my internet connection that I am not aware of.