Mordekaiser Ult Bug

I've been playing since Season 3 and I've noticed within the past month a bug to his ult. It seems that half of the time that I use Children of the Grave and the target dies, the soul/clone doesn't respond to my commands. I know I'm doing it right because I've played hundreds of games as . The bug has cost me important objectives that I couldn't achieve because the clone died right away. It doesn't move, it just stands still and auto-attacks the nearest enemy, not even the one I tell it to target. Will this bug be fixed soon?