RPMs with non-zero epoch have missing epoch attribute in <rpm:provides>
element of the primary.xml database. This causes yum to fail during depsolve when such packages are being used.
Specific case: I have a subset of packages from official centos7 repositories that I keep in a hosted yum repository. The failing package is dhclient (which uses epoch value "12"), resolved as a dependency of NetworkManager.
Comparsion of primary.xml from nexus with the one created by createrepo shows the differences. Both files are attached.