Slide in plugin corrupting XML sitemaps

Just wondering if this has come up with any other users. When Slide In plugin is active on my site, sitemap links fail, with a message: XML Parsing Error: junk after document element.
I'm using Yoast SEO, but I also disabled Sitemaps with them and tried Jetpack Sitemaps. I get the same message, XML Parsing Error: junk after document element. As soon as I disable Slide In plugin, sitemaps work again. Note: I am only using one plugin to generate sitemaps. I disable each one for testing and presently have just Yoast SEO running again for my sitemaps.
I do like the Slide In plugin, but I'll just disable it for now. Any tips or suggestions; something in the Slide In settings I can tweak?