Renaming Bug:
Replication Steps:
1: /give @p command_block_minecart 1 0
2: place anvil down and rename it "TEST"
3: place on track and type in a command ("/say hi" for example)
4: when we do "/tp @e[name=TEST] @p", it will work!
5: Now break the minecart. It is named "TEST".

6: put another "TEST" on the rail
7: save and exit world. and then reload world.
8: try same command "/tp @e[name=TEST] @p", it will NOT work!
9: the name disappeared.
Still in creative mode, left click the commandblockminecart to destroy it. IT WILL DROP AN ITEM! any other minecart WON'T!
AND it is named "@"

*10: But when we do "/summon MinecartCommandBlock ~ ~ ~

" IT WILL KEEP THE NAME!*

little summary:
1: Renamed commandblockminecarts in anvil, when broken, will drop minecart WITH the name given to it (Pre: "TEST", Post: "TEST").
2: Renamed commandblockminecarts in anvil, when broken AFTER RELOADING WORLD, will drop minecart WITHOUT the name given to it (Pre: "TEST", Post: "@")

3: Summoned named commandblockminecarts, when broken, will drop minecart WITH the name given to it regardless if the world is reloaded or not. (Pre: "TEST", Post: "TEST").
EDIT 4: Renamed CommandBlockMinecarts DROP ITEM in CREATIVE. which it shouldn't!

I hope this will be fixed soon so that command_block_minecarts always remain their names!!!

I tried to explain it as best as I can, here are some screenshots aswell!