Tahm and the weird spitting

So recently when i am playing tham and i q-w to eat a minion... well when it's a caster minion ... when i spit him out to throw at my enemies and stuff he doesn't do that (about 1/10 times) he just appear right in front of me doesn't splash at all he stands there and slowly disappear (he makes no damage either) which can be annoying when you rely on them to poke i don,t have a video because i don't remember at the exact moment it happened in my games

EDIT : there is the proof https://www.youtube.com/watch?v=AlW81WueVFY&feature=youtu.be