Following advice from various people, I decided not to avoid specific updates that prevented the export from working. I used the export for security backups, and I now copy the contents of
C:\Users<my user>\AppData\Local\Microsoft\Windows Live Mail
to my backup locations. '<my user>' is the name of my actual user on the PC and will depend on what user name you are using.
To restore emails, I open WLM in one window and File Explorer in another window alongside. I make sure I have an empty folder in the WLM window (normally I empty the 'Deleted items' folder and use that). Then I drag as many .eml files from the backup locations in File Explorer into the empty folder as I want. I can then review the emails I have restored. I move those I want to keep to more appropriate folders and delete the rest of those that I restored.
Although 'exporting' emails by copying the contents of the folder above does add a few extra MB to the backup size, it is very easy to implement. I have set up a favourite in File Explorer that takes me directly to the folder indicated above where I select the entire contents and copy those to the backup. The whole backup process is entirely in File Explorer.
I suggest you look at the details of the updates you are avoiding to see if they are likely to leave you exposed to other security issues.