Hello,
Even with 7.2.7 firmware, TCR100 has only about 4.1 MB for additional packages, the rest of flash being occupied by the firmware.
Executing the following command in the CLI/SSH terminal
might help to spot directory, taking up the most space and then you could try to empty it.
If no specific configurations were made, and you have no packages installed, you could try to simply reset the device to factory default configuration (System -> Backup -> Restore default settings).
Best regards,