Sorry Dennis, you are correct.
I just realized that we don’t have that option for deleting posts by duplicate title. The reason being the addon has to scan the entire db to figure out duplicate titles.
You said you have about 410,000 posts. Can you also tell me approximately how many duplicate posts would be present?
This addon uses two queries. One to find all posts with duplicate title and one to delete them. I also need to know which one is failing. Will it be possible for you to give me access to your WordPress installation?