Vayne/VI bug

I do not have a screen shot but I am sure this is easily reproduced.

VI from what i remember has an UNSTOPPABLE ult. now. vayne has an e, from what I understand. is not unstoppable and therefore the unstoppable ability should take priority, I get weird interactions from 2 unstoppable abilities.

Ults caught out E's towards the end of ult. pushed back inches away from stuck in the air slamming into nothing..(no damage either) walks away happy

this is not the interaction I think should happen. even if Vayne ult q'd I would understand, because stealthy vision loss = lost target (not counting bushes) however. Should That E not have taken effec after the ult? or only applied the damage? I am sure this is a bug