Even if the build configuration would not have changed there has been syncrepl interop issues between different releases in the past. So I would not expect this to always work.
There was an issue with ppolicy in one release, but outside of that nothing that I'm aware of. ppolicy needs a bit of work to fix its current mix of external and internal schema which would resolve such issues long term, but isn't a problem with other portions of OpenLDAP.
--Quanah -- Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: <http://www.symas.com>