Firmware update broke My Cloud Mirror Gen2

Hey there

A few weeks ago my Cloud Mirror Gen2 stopped working.
The power light keeps blinking blue, while the two bay LEDs are solid blue.
I have tried both reset options with no success.
The Dashboard is not available, but the device is visible with IP-Scanner.
Sometimes after a few hours the lights change: the bay one LED turns solid red, the other two stay black. In this case I’m able to login to the Dashboard but it stays unresponsive.
Since the warranty ran out one month ago I have to fix it myself.
I’m pretty sure that a firmware update screwed things up (thanks WD!).
There must be a way to perform a manual system recovery, something in the line of what he does with the his WD MyCloud: https://www.youtube.com/watch?v=0OrtHp4eGKI&t=145s

Please help and don’t tell me to try a reset, see if the power cable is connected correctly, the LAN-cable is broken! I have tried all that stuff…
Thanks for your advice