Does this "identifierForVendor" change depending of what?
from my Iphone, two identifierForVendor:
308CA132-293A-44E7-93FF-ACBF24F205AC
55140AB0-77E6-4DF3-B1D0-8D353A4C8771
All installed apps from one developer will have the same identifierForVendor.
If you delete all apps from this developer und then reinstall them, the identifierForVendor change.