Tahm Kench make minions immortal [gameplay]

When playing Tahm Kench and select too eat a minion with the W, after the minion can becoume immortal. The minion lands just infront of Tahm Kench when trying to throw it against something. After landing infront of him the minion can not be damaged for a while. I would guess the immortality last about the length the minion could stay in the stomach after eating it. No minions, camp or tower can harm it even if it gets more than enough damaged to be killed.

1_: Eat a enemy minion (ability W) 2: spit out the minion _ 3: now the minion is immortal for a while

This has happened 3 times in 2 game that was played after one another, at least what was detect. Have only played without skin so i have no ide if with skin the bug do not exist.