Hi Scott,
The safest way forwards with this isssue is to first do a backup (Export) of your music collection to an external USB device. That will secure your collection outside of your B2 in case of further actions being required. If you are compressing to 'flac' format then your collection will be about 240GB in size and the 'Export' will take approximately 9 hours to complete. The 'Export' can be done with 'HDD read only' showing, because the internal HDD is only being read from during this operation.
The backup function is found in the front panel menus at 'Main' --> 'USB Functions' --> 'Export to C' (if using USB C port) or 'Export to A' (if using USB A port).
The USB device must be formatted as 'FAT32', no other format such as 'NTFS' or 'exFAT' will work.
If you have to format the USB device, the format function is located at 'Main' --> 'Settings' --> 'Maintenance' --> 'Format USB C' (or 'Format USB A). Note: Do not use the 'Format HDD' function under any circumstances at this stage; this function will delete your entire music collection from the B2.
As Daniel has stated, often the 'HDD Read only' is caused by a corrupted track on the B2's internal HDD. Let us know how you get on.
Regards,
Peter.