Hello Neilshahlimited, I am sorry to hear you are having problems with your system.
It seems like you already performed most of the troubleshooting we requested to customers.
I would like to know which the current BIOS version of the NUC is and which was the previous one?
I’m going to make some tests on my NUC. I’ll keep you posted.
I'd recommend using the driver from here BT_17.1.1406.01_e164.exe
1. uninstall current driver
2. Cold boot (important step)
3. Install the above driver
This could be reconnection issue. This particular mouse disconnects on idle.
>> I restarted the machine and from then on they have both failed to be recognised when I try and add a device
You should pair the devices only once