I have this black screen during the calls as well. I just downloaded and installed the update 10.0.2 for the teracube one. I wiped the cache and did four factory resets, and i lost count of the restarts and nothing has worked. The one thing that has provided a little help is that I press firmly on the top 1/3 of the screen and it turns on for a nanosecond, I have to be quick to put it into speaker.
However I do not always want to be in speaker or with headphones in.
I really do not like this bug, any updates on possibly fixing it? @Sharad