If the unit is covered by a support contract and this is service impacting, your best bet is to open a support case to investigate the issue live.
Most common reason for a unit to behave like this is if you have a VLAN failover enabled, and unit has the monitored links down.
I haven't seen this specific evidence in your logs, but you do have a deamon heartbeat failure error. That means a system process is failing to respond to HA daemon heartbeat messages, which triggers the failover.
Again, I'd suggest you have support look into this.