There is a trouble with horses and minecarts.
The problem is what horse is much bigger than minecart, and if it enter into it You can not release it, because when you trying to punch minecart, you punching horse.
The only way to destroy minecart, it's dig down and punch it from the bottom, but after this my horse becomes laggy and "fall" trough 1 block down (Screenshot available)
Screenshot 1 - Trying to release horse, but punching it.
Screenshot 2 - Bugged horse after releasing from minecart.
Sorry for my bad English, and thanks for keeping amazing game amazing!