I am trying to tasmotize 2 x Sonoff ROWR3. They are based on ESP8266EX.
With both device, tasmotizer stops usually at around 43-44% in the backup stage. Most of the time it would give a message that it got corrupt data expecting 0x1000 bytes but received 0xe10 (or another number, this changes at each trial I did). Some it just hang.

While writing this I did more test. Eventually realized that the issue might be USB, whic was connected via a USB hub. I connected directly on the computer and the problem was gone.

SOLUTION
So, if you ever get an error during the backup (and presumably during erase or write) and use a USB hub, simply bypass the hub!!