Thanks to Vedder and gang, the latest firmware update fixes the issue I was having with using an NRF51 module using the previously available firmware.
If you have had the issue where you can flash the firmware and then connect but it gives a no firmware read error I believe it will now work for you if you update the firmware again.
I have tested on 4.2 and 5 beta 7
The latest firmware is integrated in the latest 5 beta package, can flash using that vesc tool
You can also upgrade using 4.2 tool, just load it in custom