Take a minecart and change it's name by using an anvil.
Place it and make sure it is near you when using the command below.
Teleport it by using this command: /tp @e[r=10,name=<name of the minecart >] ~ ~30 ~
It will work.
Close the world and open it again.
If you try to teleport it by using the same command, it won't work.