Error in LoPy firmware upgrade when using local file for both cli and gui (Linux)

[agotsis]

I have the following setup in Linux: Pytrack (firmware fully updated) + LoPy (the old one, not LoPy4).
I tried to update the firmware of LoPy using a local tar file downloaded from https://github.com/pycom/pycom-micropython-sigfox/releases but failed.
I used both the GUI and the CLI versions.
For CLI I ran: sudo pycom-fwtool-cli -v -p /dev/ttyACM0 -s 115200 flash -t /path/to/file.tar.gz and got

Running in PIC mode
Product ID: 19 HW Version: 3 FW Version: 0.0.8
Connecting.....
Uploading stub...
Running stub...
Stub running...
Invalid script command f

For the GUI method I got the error shown in screenshot.

Cheers