[GAMEPLAY] Rengar Ultimate bug

I know you guys probably won't do anything about this, as the new rengar rework is due to come out soon, but there is a bug with Rengar and (I believe) Youmuu's Ghostblade. I was just in a game as rengar, and if i ulted THEN activated Youmuu's Ghostblade, it would delay the stealth as if i were taking damage, but i wasn't taking damage. This happened multiple times, and got me killed every single time. I can pull a replay from Replay.GG if necessary.