Jetson TX2, jetpack 4.3, flash stuck at 99.8%

I’m a trying to flash a Jetson TX2 with Jetpack 4.3 via SDKManager.
My host PC is an standard Ubuntu 18.04.
The board is mounted on an Auvidea J120-IMU Carrier.
It was very difficult to put the board in recovery mode (*), but in the end, I succeed in the operation. However, the flashing operation gets stuck at ~99.8%. After two hours I removed the cable, and SDKManager immediately detected a “connection lost”. I retried a second time, same issue.
What should I check?

(*) despite pressing the buttons in the correct order, SDKManager answered me more then ten times that the board was not in recovery mode.

Are you using a charger cable for the micro-B USB? Quite often charger cables do not work well with longer data transfers and are cheaply made for charging instead of data. You could provide logs of the flash, but the first thing I would do is make sure the cable is high quality. I don’t know what other carrier board manufacturers do, but the the micro-B USB cable which comes with the dev kit is actually far higher quality than most charger cables. If the manufacturer does not provide such a cable, then consider trying several different brands of such cables (and not ones marketed as just charger cables).