So it doesn’t seem that this plugin’s preloader is compatible the xml sitemap created by XML Sitemap Generator for Google from Auctullo (I can remove the link if it’s against rules here, just added for convenience).
My site is very large (130,000+ posts) and the default sitemap or yoast sitemap are impossibly slow to load, so much so that google says it can’t read them. The one from Auctullo works fine though and loads much faster.
When I start the preloader, it only runs for a few minutes (I can tell because I can start it again maybe 5-10min later and it doesn’t give the error that it’s already running). However with 130K pages, I would expect the process to take a week or more.
Any chance you can add support for that xml sitemap?