Consistent getting kicked from server when attempting to ride minecart/boat and presumably pig saddle

Whenever someone tries to ride a boat or minecart the rider gets disconnected from the server immediately with the server logs stating that it "dismounts player" however, when said player tries to log on to the server again it will just consistently disconnect them from the server until the rider has been removed from the rideable entity by some way or another, usually by reloading the server in 1.5.1 and then making them dismount there.