Sivir Spellshield blocks two of Vel'koz's abilities if they hit simultaneously.
- Vel'koz hits sivir with q (one passive stack applied)
- Vel'koz casts W and E.
- Sivir spellshields
- Both spells hit simultaneously.
- Sivir still only has 1 stack of Vel'koz's passive on her.
I'll see if I can reliably reproduce this bug later.