Thanks for the above. I should add that the first step (formatting without removing the bootloader) is critical to making this work. I tried to just flash the pre-loader and then the operating system second and the phone was bricked.
So again, that first step is critical.
I flashed the 20160822 Android 6.0 update and then did a local update to 20161025 Android 6.0.
My main aim was to get back to the latest version of Android 6 due to the Capacitive button problem with Android 7.0 (which seems to be largely ignored by Blackview).
Whilst the performance of these buttons is better under android 6, they still aren't great. They go to sleep easily and are hard to wake up at times. I have found by tapping the PTT button it wakes them back up. Maybe it's a safety feature, I'm not sure.
When I opened up my phone I noticed that the case was dated December 2016 so this was no doubt constructed later in the BV6000 distribution. I'm thinking that Blackview has swapped out the original capacitive buttons (Home / Back / Menu) for a cheaper version (to save on costs of the production of thousands of phones) and now it's starting to show. This might explain why some people are experiencing this problem and others aren't. Having said that under Android 7, Glove mode worked too well. Very sensitive. But without Glove Mode they were virtually inoperable at times and always very unresponsive.
Under Glove Mode (Android 6) the buttons seem to be just as unresponsive and the glove mode option doesn't work at all now.
I'm quickly coming to the conclusion that this won't be fixed or there's something sincerely wrong with the adaptation of the android operating system to this phone.
Not sure what the answer is