Vel'Koz ultimate

Was playing kalista earlier today ,enemy team had a vel koz mid. Around 30 minutes in we have a team fight,he uses his ultimate and it deals 0 damage to everyone on our team. I literally walked in and out of it constantly for the entire duration and took no damage at all. It happend again around 5-6 minutes later in another team fight and he again did 0 damage. Enemy team and my team noticed so it wasnt just me.

Sorry i took no screenshots or proof but if it helps; Our team: kalista blitzcrank viktor gankplank rammus Enemy: vayne alistar vel'koz darius nocturne

Maybe it was an interaction with one of the champions that caused it so yea check it out thanks