Ok. After checking again i now see that my entire library (17k tracks) has been added to my Inbox. This happened without any interaction from me, so I suspect it's a bug.
Setup:
My music is stored on a NAS and connected by ethernet to my Windows desktop where MB is installed.
Steps:
1. Woke PC from sleep
2. Shortly afterwards I launched MB. At this point my Windows desktop was available, but some services were probably still initialising (e.g. connection to NAS drives)
3. MB GUI appeared, then i saw the library change from listing all my tracks to an empty library.
4. Restarting MB and my PC did not repopulate the library.
I actually had something similar happen about 6 months ago, but i can't remember the specific details.
I could simply add everything from the Inbox to my library, but i'm a bit concerned that something is not stable. Another option might be to reinstall a clean copy of MB, but then i'd have quite a bit of manual work to personalise it again. Considering that i've been updating versions of MB on top of each other since v2 do you think it would be a good idea to go the fresh install route?
Regarding backups, I do have some but they are older than I would like to restore.