I have a tamed tusked elephant that I have been writing. I once mounted it and was unable to control the elephant or dismount. I found that I had to use /kill (I was in creative mode) in order to escape. I have been unable to replicate this.

Also, I have a suggestion that you shouldn't be able to hit your elephant when riding and swinging with a sword. I found that you can't hit grizzly bears or komodo dragons, so I would like it if elephants worked the same. Also, I found that the elephant charge move doesn't do too much damage (2-3 hearts to zombies). If this is intentional it's fine, but increasing the damage would be pretty cool, so it could be useful in PvP.