[GAMEPLAY] Sion- Ultimate instantly ending

I have had a few games playing Sion where my ult will instantly end as soon as I cast it. I am using the warmonger skin so i don't know if it is a skin bug or a Sion bug.

1. Activate ult
2. not instantly letting go of ult button
3. ult stops instantly It happens at least twice a game if not more depending on how fast my fingers can get off the r key.