DJI Phantom 4 firmware update stops at 92%

When I update the DJI Phantom 4 firmware with DJI Assistant 2 most of the times the update stops at 92%. If I turn off the DJI Phantom 4 and turn it on again the rear lights blink fast yellow (or fast white), and the DJI Assistant 2 application cannot recognize the DJI Phantom 4 anymore …