So I've been looking into this for the past few months. I think the actual problem is a malfunctioning outside camera. Either the camera is donzo, or the connection could be loose. The black screen comes from it being unable to track I believe? And the casting to your phone to be able to see I think tricks the headset somehow into not needing that tracking? I'm not sure, the last part is absolutely spitballing. But if you warranty is over I'd look into maybe cracking it over and checking out those camera connections or sending it off for repair.
