[GAMEPLAY] Jhin Bug W Passive

I play Jhin fairly regularly and this bug comes up a lot. The W passive mark will show on them & I'll hit them - the impact & damage is clear, and my DFT will start ticking-but they're not rooted and I dont get my speedboost. Usually I notice this particularly when I see someone floating around on the enemy team with a mark that I KNOW hasn't got hit recently. Unfortunately, I'm not sure how to reproduce the effect; HOWEVER, it occurred after she had been marked, rappelled, and died after dropping back down from the rappel. The next time I saw her & every time after that she continued to have the mark, regardless of damage. This wasn't the only instance in that match where it occurred but the most visually clear one. I can highlight the other moments if you would like. I know in recent memory that I've also seen this passive W bug on a Syndra. I dont recall when in the match she started having the issue and if it was pre or post zhonyas.