thank you @rik for this first solution.
I tried successfully a second solution:
-
(re)unlock bootloader → How to Unlock the Bootloader of your BraX3
Mine was already unlocked but I did it again to reset the device. -
reinstall IodeOs using fastboot → How to manually install or update your OS on your BraX3
-
lock the bootloader
-
reboot and install OTA with IodéOs gui
It just works