[GAMEPLAY] Heimerdinger Ult does not go off

(You can see my key strokes in the gif) When you are playing as Heimerdinger and you quickly E-RW (stun-ult rockets) almost 100% of the time, heimers ult will not go off .

1. Get Ult
2. Cast E, then quickly afterwards cast RW
3. Normal W goes off, R doesn't

I've tried this over 10 times and this happened each time. Sometimes the W will shoot, and then your Ult comes up.