Veigars wall with shens dash

So veigars wall is meant to stun anyone who dashes through it or try to pass through it, etc, however that doesn't always happen with shens dash. There will be points where shen will be able to dash through the wall without being affected at all. It seems that even if animation of the wall finishes forming for a brief few seconds there's a window in time for shen to dash through it without getting stunned.