It appears that a single URL is being referenced across multiple XML Sitemaps.
Why is this important?
XML Sitemaps are instrumental in indicating to search engines the pages that should be indexed. They can be incredibly revealing especially when paired with analytic tools such as Google Search Console, in assessing the indexing status of the URLs that have been submitted through sitemaps.
<img alt="Example of Sitemap Indexing in GSC" src="path-to-your-image.png"/>
Inclusion of a URL in several sitemaps does not typically pose a problem; however, it can lead to confusion in the data reported by Google Search Console's 'Sitemaps' feature.
Occasionally, having URLs listed in multiple sitemaps could actually indicate an oversight where other URLs may have been inadvertently omitted from your sitemaps.
What does the Optimization check?
Loud Interactive's analysis will flag any internal URL that recurs in more than one XML Sitemap.
Why is this Optimization marked 'Insight'?
At Loud Interactive, we label this kind of observation as 'Insight' because it isn't inherently problematic nor detrimental to SEO or the user experience.
Even though it may be rooted in a misstep or could potentially render certain reporting tools less efficient, we bring it to your notice for further scrutiny that you might find necessary.
A robust approach to XML Sitemaps and index management is a key strategy for ensuring your content is efficiently indexed (refer to the 'Further Reading' section below).