Broken URLs: Year added to short URL format?

When I copy the permalink from a previous post on my blog and paste that into the text box in the visual editor (as when I’m creating a set of links to past posts for readers to check), all the info displays correctly and the title and underlying URL for the link look fine.

However, WordPress truncates the URL, dropping the domain name so that the actual pasted permalink looks something like this:

‘a href=”../2009/02/post-title/”‘

In theory that should load fine, right?

The problem is that when WordPress reconstitutes the link when the page loads, it ends up like this on the individual post page and in the feed:

‘https://domain-name.com/2009/2009/02/post-title/’

WordPress has appended an additional “/2009” to the front of the URL rather than just reinserting the domain name of the blog by itself. Obviously, that breaks the link.

Oddly,the main index page does not show the link with the added “/2009”, so it views fine, but clicking through to the single post or accessing the feed loads the URL with the added year info, thus breaking the link.

Why is this happening, and how can I fix the problem?

Thank you in advance for your assistance.