I Found A Solution That Works For Me For This Problem Because It Is Happening On All Of My Domains.
Under The Sitemap Content Options Deselect Every Option And Save The Settings Then Rebuild The Sitemap. Then Select The Options You Want Under Sitemap Content And Rebuild The Sitemap Again.
The Automatic Build Will Work Fine After That.
I’ve Tested This On 18 Sites That Were All Having This Problem And So Far It Has Worked For All Of Them.
Hope This Helps
