you have to watch this video:
https://www.twitch.tv/videos/130065685
there is a russian guy playing and his teammate says that he's near him and he see him but he actually not because of desync i guess. then he punches the wall and get's thrown back.

I twice experienced invisible infected shortly after killing one (with an arrow to the head of course).
It was almost as if the infected's ghost was haunting me.

All the best,
Trevor.

Sometimes u can gain "invisibility" using cars... but there is one important thing. u can go any place or way, do anything, but other players will see your body near car that u visited before and can kill you, or hurt you. This is huge problem with cars and invisibility

I would 2nd what @TrevorWithTheBow said.

Atleast once I have shot a zombie and had an invisible zombie hit my friends and I. To kill it I shot the body of the one I killed and it stopped hitting us and making sounds.

If anyone else has this happen to them try to shoot the zombie that's already dead and make sure to record the bug!