Serious Firmware upgrade issue in HA

[Belgarioz]

Hello,

I have several HA Fortigate managed by a central FortiManager. All those FGT has 5.2.10 firmware release and we planned a scheduled update of all FGTs using FortiManager.

following fortinet upgrade steps 5.2.10 -> 5.2.12 -> 5.4.10 -> 5.6.7 we decided to upgrade one FGT HA. The upgrade until 5.4.10 went fine, but when we pushed the 5.4.10 -> 5.6.7 update we had a serious problem: the update has been pushed to the slave (as it should do), but it wasn't pushed to the master. As a result we had a huge packet loss after the slave rebooted. We had to ask the guy who was on site to power off the slave. Then the master went up and was NOT updated (it has 5.4.10). With the Slave still powered off we forced an update to the master. Then we powered on the slave... and everything went fine.

We tried the update to another HA cluster yesterday, and it did the SAME!!!!!

Clearly 5.4.10 -> 5.6.7 gives our firewalls many problems while updating: slave not pushing (or signaling) the update to the master.

TAC gave us some troubleshooting using console, but we can't do it: firewalls are scattered around European countries. It's complicated for us because on site tech guys are not prepared.

I don't know what is going on: previous updates worked like a charm.

Is the upgrade path correct? Anyone else is having this issue?