More context: That bug that I linked (Which is a bug in certain keepalived versions) only manifests if you have more than two L3 agents participating in the HA router domains, which would explain the behavior that you're seeing. If you look at /var/log/syslog or messages, if you're using a 'bad' version of keepalived, you'll see that keepalived is flapping between backup and master.
More context: That bug that I linked (Which is a bug in certain keepalived versions) only manifests if you have more than two L3 agents participating in the HA router domains, which would explain the behavior that you're seeing. If you look at /var/log/syslog or messages, if you're using a 'bad' version of keepalived, you'll see that keepalived is flapping between backup and master.