[Gameplay] Vel'koz ult stops immediately after using combo

This bug has happened for like a month or so its now a pain in the butt. Either way, When I use Vel'koz's full combo ,e w q r, As soon as I hit r, the ult stops immediately. This bug only happens when I use quick cast and it seems to only happen if I use q before I use r. I've tried this in custom games and it seems to happen nearly each time. I tried other combos like q e w r and it all seems ok as long as I don't use q before r. I wish this bug would be fixed so I can use the e w q r combo and not worry about the ult stopping.