Hi @tooz:
I use Tinker_Edge_R-Flash_GUI_V1.0.0 to flash "Tinker Edge R Debian Stretch V1.0.13" still failed.
But it worked by @Kubo method to enter ums mode and Start Etcher to Flash the image("Tinker Edge R Debian Stretch V1.0.13").
Can you help to update Tinker_Edge_R-Flash_GUI_V1.0.0 tool or image?