Severe Semi-Rare Bug with Velkoz

A few times in my past games I've had Velkoz's ult do absolutely nothing when cast in quick succession with his other abilities. What usually happens is I will Q for the slow, and then roll my fingers across WER (in that order) to get the rest of my combo off. However, this rarely (<10%) results in my W and E being cast, but my ult going on cooldown while doing nothing. If it happens to a support Velkoz right at his level 6 powerspike it basically dooms him for 2 minutes.