duplicate namespaces from moc 1 out of a few hundred times

We are randomly seeing compilation failures that are the result of seemingly invalid moc generation.

Have not been able to find an easy way to repo. But when the problem a few dozen of the follow changes are seen in the output moc

bad file

-const QMetaObject &my_namespace::my_namespace::my_plugin::getStaticMetaObject()

{ return staticMetaObject; }

good file

+const QMetaObject &my_namespace::my_plugin::getStaticMetaObject() { return staticMetaObject; }

Eventually resulting in c++ compilation error
error: 'my_namespace::my_namespace' has not been declared