Permanent Shaco clone

I have found a bug when playing with a friend. I was playing Shaco and I decided to build magic resist. (Spirit visage, mercury's treads, banshee's veil, warmogs, mercurial scimitar and titanic hydra) when I ulted with this build as Shaco my clone would appear but if he hadnt lost any health he would not die, wich lead him to becoming a permanent clone for me. I was playing on Howling abyss btw.