Unable to set entity again as a passenger for 3 seconds after calling eject() method.
Reproducing:
[code]Sheep sheep = (Sheep) player.getPassenger();
sheep.eject();
Bukkit.getScheduler().scheduleSyncDelayedTask(this, new Runnable() {
public void run()

{ player.setPassenger(sheep); // Doesn't let me to set the sheep as a passenger for 3 seconds. }

}, 20L);[/code]

What I did to get around it temporary:
[code]Sheep sheep = (Sheep) player.getPassenger();
sheep.eject();
Bukkit.getScheduler().scheduleSyncDelayedTask(this, new Runnable() {
public void run()

{ sheep.remove(); Sheep newSheep = sheep.getWorld().spawn(sheep.getLocation(), Sheep.class); player.setPassenger(newSheep); // Works... }

}, 20L);[/code]