Thresh Hook not working on Undead Sion (Post passive proc) [IN GAME]

Sorry, have never submitted a bug report and didn't manage to snag any screen shots of it.

I just played a game as Jax jungle, with a support Thresh on my team and a Sion in the enemy teams top lane. On two separate occasions after Sion would proc his passive and respawn in place, Thresh's hook would not be able to connect to him. Once this happened in the center just above river in top lane, and another time while pushing down their middle inhibitor. Sion would get up, run around for a second or two to hit things, and then Thresh would throw the hook (So he definitely wasn't just throwing it too early when Sion was untargetable)

The hook would disappear and the Thresh animation would cancel the second the hook got to the frame where it typically generates a positive response, or in other words the second it "hit". It would put the hook on CD for Thresh but again would have no effect on either player. Both the enemy Sion and our Thresh noted that this was occurring and that it was "odd". Sion believed he should have been hooked both times, so does Thresh and so do I. They were direct hits - not even the kind where it was a "max range maybe on the right side of the hit box" type things. Half the hooks total range, direct hit to the chest, resulting in the hook disappearing, the animation cancelling halfway through, and the CD being procced.