• @user94443 This command line you're using:

    esptool.py -p /dev/serial0 write_flash 0x1000 espurna-1.13.2-itead-sonoff-th.bin

    Is that Espruino? Or something else. It looks like "Espruna", which is not related to this project at all. The only thing I can recommend is you get another ESP8266 and see if you can replicate the problem. If you can't, then suspicion falls on the original board.