[Gameplay] Tahm Kench W - Devour Bug

Tahm Kench W - Devour when you use it on a minion it sometimes makes the minion invurnable to damage for some seconds at first i though it was ping but then it happened more without spikes on ping so i assume its a bug it doesnt happen often and i am not sure how to reproduce it my thought are that if u dont throw the minion and you hold it in it happens or maybe it happens randomly thanks for your time.