Comment 16 for bug 1798475

So, that "forcing new election", "Received advert with higher priority 50, ours 50" can be caused by this:
https://github.com/openstack/neutron/blob/master/neutron/agent/l3/agent.py#L277-L280
It will set the HA port down during the L3 agent restart, sometimes that can unexpectedly cause VRRP re-election.
Yes, I've tested it without such behavior: https://review.openstack.org/#/c/627285/.
The fullstack test was passed 17 times.