[hurricane51]

So...that seems to tie this up. Agreed? (I'm pretty sure you'll be happy to sign off.) 

I can only repeat that if you are getting unexpected behaviour then I am happy to pursue it with you, but it is up to you. If there is a bug then I want to find and fix it, but having repeatedly tested I can not reproduce any issues.

I am still confused by exactly what you are reporting - first artist NFO were "deleted" or "missing" but the files were actualy overwritten with different data (which is a totally different issue), now artist.nfo are fine but album nfo are "missing" (only getting 56 out of 1200 albums).

How are you accessing what album.nfo are produced by export? Do you not already have many album.nfo sitting there (previously restored from your backup) hence only 56 new ones created with overwrite disabled?
 
A look at your MyMusic72.db could be informative, post it on the cloud somewhere and PM me a link. That would be my next investigative step, but if you do not want to pursue this then that is fine too. 

Sorry to take so long to respond.

As a test, I deleted all of the NFO files in my library, since I had a backup. I ran an export and KODI only created 56 album.nfo files. Now, all albums do not generate album.nfo files, but in my backups I have about 350 album.nfo files.

I'll watch what happens in subsequent exports, but it's the artist.nfo files I'm most concerned with and that's straightened out. Tagging the media files pretty much takes care of the info that the album.nfo files contain.

That's when I meant with "that seems to tie this up". And that's my feeling. But I learned a lot from this thread and I appreciate the help provided by everyone who contributed.