I attempted to herd some sheep and a cow into minecarts to transport them via rail to a distant location. I was able to lure them into the carts--a cow and a sheep each in their own minecart, with me in my own minecart behind them pushing them along the rails. The trip along the rails began successfully.

Then, quite a way down the track, the livestock began to take damage for reasons I was not sure of (they had clearance space, no mobs, etc.). They soon after died / flat-out disappeared. Discouraged, I continued solo in my sad minecart toward my destination, and soon the sheep and cow began to pop up in the middle of the tracks just ahead. Like "ghosts" they floated just above the tracks (as if in invisible minecarts), and did not progress along the track. I could walk right through them and they could not be struck by hand or weapon. Upon turning my back and looking again, they vanished.

After getting back in my minecart and progressing again, the same ghosts appeared a little way down the track. And this "ghost appearance" continued over and over. Haunted by the sheep I tried to herd. The minecarts also started to move on their own: I had about 5 minecarts pooled on the tracks near my destination and they began to run on their own, as if occupied and triggered to move (the powered rails activated as if the cart was occupied). An imaginative person might think they looked haunted. (Ooooh!)

Steps to Reproduce:
1. Guide livestock (sheep or cattle) along a lengthy stretch of rail in minecarts 1-2 times and see if they make it successfully.
2. Should they make it successfully, killing them during such a rail trip may be necessary to trigger their "ghosts".
3. Ride the rails to watch for them. Watch for empty rail carts to behave strangely.