It seems like if you execute the combo too fast or if you Q an enemy right before doing the combo, attempting to do the R-ally + W combo will cancel your W and the ability will get on cd.
Maybe there is a link between the fact you Q just before using the combo (So the game may understand that you are doing the Q-R combo on enemy so he blocks your W).
I have recorded the bug, just tell me how I can send you the video.
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