Tahm Kench W cast on allied champion bug [GAMEPLAY]

So I was playing Tahm Kench in the botlane (with sivir as my adc) vs an ezreal adc and another Tahm support when I noticed that, after a certain period of time, I wasnt able to W sivir anymore... ever... for the rest of the game... I tried W-ing other allied champions, which did work. I was however still not able to W Sivir. I don't know but I think this bug might be related to either Sivir's spellshield (in some way) or the other Tahm applying stacks on sivir, which might have bugged my W out?

I tried resetting smartcast several times but I still wasnt able to W sivir.

I however was able to W sivir at the start of the game, meaning that the bug only appeared after a certain point in the game. The last time I was able to W sivir was just before she died to a dive to ahri (at 8:34 minutes)

Matchups (dont know if they matter):

Bot: Tahm Kench (me) + Sivir vs Ezreal + Tahm Kench Jungle: Shyvana vs Rengar Mid: Ezreal vs Ahri Top: Lee Sin vs Fizz

I really love Tahm Kench already but this game breaking bug is just really stupid...

-Troller0001 EUW