This is the funniest bug I've ever witnessed
So Rek'sai has a bugged interaction with Nunu that causes him to skyrocket off the map should she knock him up during his W, however I'm not certain if this bug is just between these two champs, or if it can occur with any champion that has a knock up. That said, I would show a recording of this bug, but problem is, the match history tool currently isn't working :/ However, here's a link to a video Vandiril made show casing the same exact bug: