Hello @dimthomos,
Thank you for contacting us, and sorry for any inconvenience that might have been caused due to that.
For initial troubleshooting, please make sure that your sitemap is not getting cached. Please follow these steps:
1. Flush the sitemap cache by following this video screencast:
https://i.rankmath.com/pipRDp
2. Exclude the sitemap files of the Rank Math plugin in your caching plugin. The cache could be via a plugin or from the server. For plugins or Cloudflare, please follow this article:
https://rankmath.com/kb/exclude-sitemaps-from-caching/
3. If the above steps don’t seem to work, kindly apply the following filter code to your site.
add_filter( 'rank_math/sitemap/enable_caching', '__return_false');
Here’s how you can add filters/hooks to your WordPress site:
https://rankmath.com/kb/wordpress-hooks-actions-filters
If the issue persists, please share your sitemap URL alongwith the affected URLs that shouldn’t be in the sitemap. So that we can take a look.
Looking forward to helping you.