I created a loop by accident – perhaps that’s what others have done, too.
I had a page called “X” and a page called “X_new”. I wanted “X_new” to be the new content for X and to rename “X” to “X_old” so that all those with references to “X” would get the new content.
In the process I tried to first rename X to “X_old”, realized that I wasn’t ready for that so I renamed it back to “X”. Later I renamed both “X” to “X_old” and “X_new” to “X” I ended up with 4 entries in the wp_redirection_items table.
Using pHpMyAdmin I deleted those four lines and it solved the problem.
NOTE: I have the Redirection Plugin, but it didn’t seem to be showing this particular loop.
By the way, I also found 44,651 records in the “wp_redirection_logs” table. I assume I should be able to delete them, yes? It looks like a great many of them list Chinese IP addresses dating to about two months ago. I was the victim of a comment spam attack last week: 65,000 attempts to post comments.