I also used terra term some weeks ago with the following steps to recover:
1. You need to set the hardware into UART mode by modifying the following pads during startup:
* Shortcut R80 (for example with a screwdriver)
* and bring +3.3V on the left side of R65 (for example with the voltage from the serial port)
If the UART is activated, you will see:
ROM VER: 1.0.3
CFG 04
Read EEPROMX
X
UART
2. After that you have to remove the shortcut and the voltage on R65, otherwise you can not upload.
3. Upload U-boot (u-boot.asc) with TeraTerm (just send, no xmodem or ymodem).
U-boot will start automatically.
After that I flashed brnboot depending on the u-boot version with ubootwrite.py, tftpd or loadx.