Tahm Kench W bug, can't eat a certain champion ??

Hello, I played a game today as a support Tahm Kench, in the beginning everything seemed perfectly normal, but in mid game, something happened to Kai'Sa, and I could no longer eat her (use W on her), like when I click W on her, it just shows the blue border. but I couldn't eat her. But I could eat other champions and objects. the only one I couldn't eat is Kai'Sa.. I don't know what exactly happened to her in the game, but what I know is I couldn't use the main ability for Tahm as a support on my ADC. Which kind of lost us the game, please try to fix this bug. Thank you