Braum's E vs Nami's Q [GAMEPLAY]

I have recently encountered a pretty annoying bug, when i played Braum against Nami/Tristana my shield happens to block only damage from Nami's Q, ADC standing right behind me gets CC'd with me for no reason at all, i mean, it isn't like Tristana's r which is supposed to push all the targets back, so when i only block damage and still get knocked back alongside with my adc that makes sense, but if I block Nami's Q why do i only block her damage? It's a projectile after all, nothing like Cho Gath's Q, you can stop it mid-air but it is still effective in some ways.