Answering questions over the years, I've seen instances where people have lost hours of work because of this.

I guess I haven't found the protected view a nuisance. I had forgotten that it could be disabled.

In Word 2016, as in previous versions, this is in the Trust Center settings under options. This is the screen you show. I have no answer as to what may be overriding that. On the user's computer when you reopen that screen are the boxes still unchecked?