Hi Gary,
Another thought for you is this. In the spring of 2020, I began to look into 'Export' and 'Import' failures, as many users were posting problems. However before I really got going I found that these functions were failing randomly on my B2 before I got to the reported problems. It took me a day or so to find that the problem was being caused by the Bluetooth dongle. I removed this and suddenly the 'Export' (and 'Import') began to work more reliably. After that, I was able to get to the real problem, which Brennan subsequently fixed. I have done upwards of 50 Export and Import cycles since July 2020 and these have worked without problems. So I regard the 'Export' and 'Import' functions as totally reliable.
So, if you have a further problem with your 'Import' I would suggest that you first remove both the Bluetooth and WiFi dongles and then run the 'Import'. Once the Import is complete then plug the dongles back in.
Also in reading this entire thread, I strongly suspect that the problems with your B2 are likely to be caused by the the WiFi dongle. I would replace it with a proper antenna based unit (make sure it is RT5370 compliant (about £10 on Amazon). My reason for suggesting this is that, in my view, it is unrealistic to expect the B2 to perform reliably without an antenna based WiFi unit. I think that when the WiFi gets into difficulty that causes the B2 to become unstable and that could lead to a number of different situations. One situation is that the B2 is very good at 'protecting' its music collection and will deliberately go in 'HDD Read only' mode if it does get into difficulty in an attempt to prevent the music prevent disk corruption.
I set up a test first using a Brennan WiFi dongle then using an antenna based unit. The Brennan unit showed at -60 to -63 dBm, whereas the antenna based unit showed at -30dBm. This is a factor of 1000 improvement in signal strength (the dDm scale is logarithmic and every -3dBm improvement = a doubling of the signal strength)
Replacing the WiFi dongle with a proper antenna based unit would be a massive improvement. My set up is two B2s, both hardwired and one BB1, wireless connected to a network of three Windows servers using NAS throughout. Then I have four Windows laptops and three MacBooks, all also using NAS. All of this runs without problems day after day. The older B2 is now over 4 years old and all three Brennans have been stable and trouble free.
Some users will be thinking 'well everything else works on my wireless network'. This is true, but everything else has a 4 to 6 inch antenna usually hidden inside the phone or laptop or other wireless device. The B2 does not have that, and thus suffers from having to work with an unrealistically low signal level.
i don't normally use wireless on my B2s and I think that this is why my environment is so stable. The BB1 is also stable, but it has (I think) an antenna hidden inside the case just like most other wireless devices.
My apologies for the length of this post but when I saw what you are suffering from, I just had to offer some assistance in order for you to get to a 'happy place'
Regards and good luck!
Peter.