I am sure there are few reasons for this, but here was my solution…

At my job I have to use Windows, but when I take my work home I use my Mac. I was having this problem when I was working on a doc I created at work, at home on my Mac.

I just recreated the doc and copied and pasted in place from the old doc to the new. I think this would also work if the doc is just an old one.

It works fine. Hope this helps some.