A problem occurs when trying to use the /fill command with tile entities, while trying to make it only replace certain blocks.
I used the following command:

/fill 136 64 -192 141 65 -187 command_block 0 replace stained_hardened_clay 0

It comes up with this message:

Data tag parsing failed: Invalid tag encountered, expected '{' as first char.

The game thinks I am trying to use /fill with a tile entity and use a data tag, but i am not.