Not my car but my wife's car. Stereo kept rebooting and also navigation was refusing to load so I immediately suspected the hard drive in the head unit since BMW used mechanical hard drives in the NBT units which seems crazy to me but there we go. Of course replacing the hard drive is an absolute nightmare.
I had to buy a replacement 2.5" SATA drive and pop it into a PC then boot it from a QNX boot CD. I then had to create 4 QNX partitions which was effort in itself because you can't just specify the size in MB/GB, but you have to specify it in cylinders so I had to calculate and use trial and error to get the partitions to be the appropriate sizes since the old drive was 200GB and the new one is 500GB.
Once that was done I had to run a script that formats them and creates a series of empty directories to prep it up. At that point, I popped the drive back into the head unit and reinstalled the maps from a USB stick and to my amazement it actually worked.
However the electronic manuals weren't on the drive so that side of things didn't work, plus I assume some other functionality may not have worked although it seemed to be ok so I thought I'd have a go at copying it from the old drive. Just to make things even more effort, the hard drive is locked with a password which consists of the head unit's Ethernet MAC address, the Bluetooth MAC address and part of the unit's serial number but in hex format. The serial number and Bluetooth MAC were easy to get but the Ethernet MAC was nowhere to be found.
I ended up having to connect my laptop to the car with a BMW OBD ENET cable which connects to a laptop via Ethernet then run a DHCP server on the laptop wait to see what leases were offered. It gave two out so I looked up the MAC addresses and identified the head unit's MAC so password was sorted.
Then actually running the app that handles the drive unlocking was even more effort but eventually I got that working, I got the security removed from the drive, all the files copied off to another HD and then I unlocked the newly built drive and copied the files back to it. All works perfectly now
Seems a lot of effort but BMW would've charged an insane amount and a replacement NBT unit from ebay would still have cost me around £200 then I would've needed an emulator or FSC codes to activate the navigation again which would be about £30 and it would still have had a 5-7 year old hard drive in it anyway. This way I got it sorted out with my only costs being £15 for a drive and a good bit of effort on my part. Also my car has the same head unit, so at least I know how to replace the drive on that if/when it dies which I'm sure it will eventually.