If you see label like Unknown234 in the sitemap, here is how to fix this.
1) Export the CRM solution as unmanaged solution with sitemap.
2) Unzip the solution file.
3) Open customizations.xml file.
4) Navigate to Sitemap area.
5) Look for GroupId tags without ResourceId. These are the cause of Unknown in the sitemap.
7) Import the solution.
Hope it helps.