I have no idea where to put this thread. It appears that a duplicate note document has been created. By "duplicate," I only mean "title." The main document has 1304 highlights. The "duplicate" has ~14.
macOS, iOS & iPadOS | Logs | Install
I was able to reproduce something like this on iOS with vNext beta. It is probably a bug in the mobile code. I'll create a case.
Mobile Development Team Lead