The snooze times for promote/demote for one or both peers is too short.
For each peer, time how long the peer requires to fully promote and fully demote (include pre/post scripts). Then add 5 seconds to each (or more depending on variability of the system performance) and set the promote and demote snooze times accordingly.
Restart HAAst and retry manual failover again. If dual active/standby contention continues then increase the snooze times in steps of 5 seconds and repeat.
