[BUG] Tahm Kench devour bugs

I have noticed two bugs with Tahm's W, devour:

First, it sometime causes enemy minions or monsters to become temporarily invulnerable. I had this happen two times on one game as Tahm Kench. Here are recreate steps:

1. Devour a minion
2. Immediately spit it out
3. Sometimes, the minion will be left with a tiny amount of life. It continues living and attacking for at least 10 seconds, completely invulnerable, until it finally dies

Second, sometimes when devourer is used quickly, it does incorrect damage. The recreate steps are basically the same as for invulnerable minions. I notice that frequently, it just doesn't apply the proper damage, especially to the devoured unit.