recurring error with xml sitemap

Hello,

Thanks for contacting us, and sorry for any inconvenience that might have been caused due to that.

Please try following the steps below to avoid this sort of issue in future.

1. 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/

2. If the above steps doesn’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 filter/hook to your WordPress site:
https://rankmath.com/kb/wordpress-hooks-actions-filters/

Hope that helps, and please do not hesitate to let us know if you need our assistance with anything else.

Thank you.