Screen turns black instead of "dimmed"

So first some background...

My watch couldn't connect to Wifi anymore. (Error 0600)

After I tried the obvious things like reboot the watch, router things like that. It didn't make any difference. So I made a factory reset of the watch.

Then after the reset the watch turns black instead of "dimmed". No matter what wachface I use. The watch only shows if I turn my wrist or press something, or if my settings is set to 'Allways on'.

Anyone that has any idea to fix this?

Latest firmware installed.