Ho lo stesso problema su più siti. Ho scritto a Tassos (ho il pro) e mi ha risposto questo:
The Schema having issues is actually unrelated to GSD, i.e. not generated by GSD.
I suggest you dig into your 3rd-party extensions/plugins or even the native Joomla Schema to disable any Organization Schema generation, and as a last resort, use the GSD Schema Cleaner to disable it.