Tahm Devour Bug.

I've started to main Tahm and I have been playing him non stop. Recently however, I had one game with him where after about twenty five minutes into the game, I could not devour my adc and save her from danger. I was however still able to devour any creep, ally, or enemy. I spent a minute spamming W on my adc and nothing would happen. It was working just fine earlier in the game. Please find a fix for this so that it doesn't happen again. Luckily my team still managed to win, but this bug could have cost us the game.

Thank you for any help.