Primary Unit in HA randomly stops passing traffic?

[duff4]

Very odd issue we've been facing over the past few months.

We have two firewalls in an HA pair. Randomly, whichever unit is running as primary will stop passing traffic. Fortinet support gave us a CLI command that will failover to the secondary device, once it fails over, everything is working fine again.

We've had Fortinet support look through things with us, they've said everything looks good. Both HA units are accessible via their MGMT IP during the outage times as well.

I've checked through the system logs each time, the only things I see happening around that time that is somewhat suspicious are external threat feed updates.

Has anyone seen a similar situation or may be able to give me more ideas of what to look for in the logs?

Thanks much!

[AEK]

Which FG model and which FortiOS version?

If it stops passing traffic then it might be conserve mode. Do you confirm?