Hello,
In this case, I would suggest updating via bootloader. Update to the 1.14.6 firmware first via 192.168.1.1/index.html. Then, you can update to the latest firmware via WebUI.
Also, from the screenshot attached, it seems that you are trying to update to 1.14.3. Please, when updating, ensure that you are using the correct file available here.
You can also try to update the firmware from the WebUI or the command line of the device itself. However, if this does not work, please, update via bootloader.
Let me know about the results.
Kind Regards,
Andzej