changes transient to expunge on cached repo instances, due to odd very rare problems with previos approach.

rhodecode/model/scm.py

@@ -180,7 +180,9 b' class ScmModel(BaseModel):'
                 .options(joinedload(Repository.user))\
                 .filter(Repository.repo_name == repo_name)\
                 .scalar()
-            make_transient(dbrepo)
+
+            self.sa.expunge(dbrepo)
+
             repo.dbrepo = dbrepo
             return repo