Try flashing couple of older versions… I would say try another set of different usb cables.
I have tried that as well.
I used multiple mini usb cables that i use to transfer data from my android, but i received the same result.
I just tried flashing it with clean flight as well but i got the same thing as BF.
I am starting to think there is something wrong with the FC!
@blackhole do you have any I2C error on your board when you configure it with BF?