Errata patches for OpenBGPD have been released for OpenBSD 6.5. Several issues were corrected in bgpd: "network" statements with no fixed prefix were incorrectly removed when configuration was reloaded, "export default-route" did not work, and "network 0.0.0.0/0" could not be used in some cases.
Binary updates for the amd64, i386, and arm64 platforms are available via the syspatch utility. Source code patches can be found on the respective errata page: https://www.openbsd.org/errata65.html