Tahm Kench bugg (cant eat katarina) and Tahm Kench devouring low life minions dissapear

Alot of times when i devour a low life minion thats getting attacked but has enaugh hp to get devoured just disappears. Link: https://youtu.be/hu5Mv6oWqRE In a game i had today i could not eat the Katarina for the whole game witch actually lost us the game. Link: https://youtu.be/KlDbBdW_IqM and https://matchhistory.na.leagueoflegends.com/en/#match-details/EUW1/3543947099/229101905?tab=overview

Apologies for my bad english btw.