Two times organe, seven times white -> LED

XPS 13 (9310)

When starting up without a charging cable or with a charging cable, the Dell logo appears on the screen, then the screen remains black and it flashes orange twice and white seven times.​  If I start the laptop with an external monitor connected, it starts normally. However, I cannot control the laptop screen (it is not recognized). In one case I managed to duplicate the display and the laptop screen worked perfectly.

What I also noticed: it can be (but is not always the case) that there is flashing (orange twice, white seven times) when using an external screen.​ 

According to the Dell manual, this blinking mode indicates a problem with the LED.​ The problem first appeared when the screen suddenly went black while working with the charging cable connected but without an external monitor.​

Thanks for any advice.