That seems like more of an issue with Deande’s ult then Kelvins sub. I’ve routinely been stunned out of subs by Montanas and Galileas (was getting really annoyed with a Montana that was knocking me out of my sub EVERY time I used it. Very good player.).
What I really want to see is 2 Kelvins sub into each other. I REALLY want to see what happens there.

one is enough