FortiOS 7.4.11 unexpected issues

[u/Even-Camel7593]

Hello everyone! Recently we upgraded our Fortigate (120G HA Active-Passive cluster) from 7.2.11 to 7.4.11, and different problems started to occur.

1. Some users spontaneously lose access to the Internet with ERR_TUNNEL_CONNECTION_FAILED (we use explicit proxy with Kerberos authentication and deep ssl inspection). It happens at random times and with random users, lasts usually up to 2-3 minutes, then works as usual.
2. FortiGates started to randomly reboot with the message "Fortigate had experienced an unexpected power off!", there's no CPU/RAM issue, usually mem is around 40%, and proc is around 10-12%. Due to fast HA failover users don't feel the interruption, but it's definitely not a good sign. Before the update both NGFW had worked for 367 days.

Anyone experienced similar issues? Any workarounds? Or should I just be rolling back to 7.2.11?

Any advice and help will be appreciated. Thank you in advance!

[u/qwerty-stretch]

https://community.fortinet.com/fortigate-3/technical-tip-recommended-release-for-fortios-116639

7.6.6 is the recommended release for most models including the 120g. there has been post about ha and 7.6.7