Comment 8 for bug 2060163

This look quite similar to https://bugs.launchpad.net/neutron/+bug/2065701 but am not sure(having debug logs and ovn-nb dbs would help to isolate) if it's same for now will tag this issue in the fix for the other one. But symptoms wise it matches as the atmosphere CI also using ovn_emit_need_to_frag = true.