When Samba has an object with multiple AUX classes in the objectClass value, these are not sorted in a deterministic way, and so subsequent dbcheck runs can re-sort the values, giving false normalisation errors.
Fixed in samba 4.5rc1 with c36b2d7fb8f10ec229bb8e6be3999ab83a26dc36 There is still no deterministic sorting (I couldn't agree a method with metze), but it no longer causes dbcheck to complain.