The behavior is according to the Sync be found in a sub-site as follows:
To solve the problem, you have to adjust the Master Page and carry out the following changes:
Change the attribute provider to Sitemap Sitemap provider = "CurrentNavSiteMapProviderNoEncode,SPContentMapProvider"
Cause seems to be the SPSiteMapProvider who for subsites probably not working correctly (SP Bug). Thismust simply replace with CurrentNavSiteMapProviderNoEncode you.