Simple Sitemaps reverting to non mapped domains…

When we build a new site and map the domain, we are sure to edit one of the pre-installed posts each of our clients gets so that the sitemap will rewrite to the new mapped domain so it reads as instead of

We’re noticing that when our users post new content the sitemaps are updating with the new content but rewriting the domain as being unmapped. We thought we saw this a few times but figured we just overlooked something but now clients that had placed tickets regarding the issue where we had fixed the issue for by editing an existing blog post are submitting tickets again as the issue has resurfaced…. it seems as though when they add new posts it reverts to the unmapped version….

Any ideas?