Double Duplicate Pages

I have used Yeost Duplicate Post plugin on the same site for many years. Two weeks ago I started getting double duplicates (ie. I would click “Clone” and 2 x duplicates would be created).

Then, when I bin one of the duplicates I get a WP notification “Error in moving the item to Bin.” but when I click back in the browser the duplicate page has indeed been moved to the bin.

I have stripped the site down to bare bones in staging (all plugins deactivated and running Twenty Twenty Four theme), and yet the issue persists.

I have also run the repair operation on database tables in phpMyAdmin with no joy.

Any ideas on what’s going on would be gratefully received.