This black screen bug has been talked about some over the last couple of weeks. I encountered it when updating to 7.17 and now on 8.4. It is so annoying and I’ve brought it up to customer support several times. Nothing we can do but wait for them to fix it. Let us know if you figure out a way to fix it, but looks like a future update is the only solution.
Yes - we'll need a firmware update to fix. I've just posted a bug report and log file to their Whatsapp channel. At least there is a work-around, and I'm very impressed with how quick it seems to connect now.