Wow. Thank you both. I didn't mean to cause this much disruption. I have been away from my computer until just now. Let me be more explicit about the "corruption" and what the current status is. I haven't tried any fixes yet and I left both computers connected to the internet with Evernote open on both of them for all these hours.
All of the files in question are web pages (documents with data I use) that I manually "write" to EN as pdf files. So, I believe you two would consider these to be documents with attachments since they each consist of a single pdf-attached file.
When the filles are created, they always have the name "unnamed document", and I then name them and move them to various notebooks. The corruption is that yesterday I had about 50 documents named "unnamed document" and which have no content. Rather, they seem to be new EN files having the prompt to "start writing, drag files, or start from a template". These files have various dates, and these dates correspond to "good" documents on the first computer.
These files were all created while using the first computer, and all are dated after Jan 1 of this year. Older files are all OK. I don't think I have opened Evernote this year on the 2nd computer until now.
As I was examining the files just now, about a dozen of them suddenly changed at once. Those files now have correct names and they moved to their correct notebooks. I still have about 40 unnamed documents left... I just looked again just now, and there are only 30 unnamed documents and 3 files that have names but no content.
I wonder if some very slowwwww sync process is strangely underway. I think I'll wait until tomorrow and if I see no further progress, I'll reread your discussion and see if I can export one Notebook at a time. An additional problem I will have is that I have move all of the subject files to different notebooks, and I have 18 notebooks. So I might have to bite the bullet and export each of the 18 notebooks. I hope not. I'll also consider creating a ticket with Support.
I still don't understand how I can have local files on my computer if there isn't a folder on my computer for those files, possibly encoded by EN. And, I should think I could just copy that folder across between computers. The computers are using the same OS (Big Sur).
Also, I observe the computer 1 has started synching EN about 10 minutes ago; it is still synching; and no files have been lost yet. So.... we'll see.