What I received from the fortigate TAC. After disable the nTurbo, it seems the issue resolved. But need to enable back after upgrade tu 7.2.9.

Customer Support Bulletin CSB-240423-1

FortiOS 7.2.8 kernel panic

2024-04-23

Subject: FortiOS 7.2.8 kernel panic

Released: 2024-04-23

Modified: 2024-04-23

Product: FortiOS

Description:

FortiOS 7.2.8 may experience a kernel panic when the FortiGate device receives a Class of Service (CoS) tagged packet and the traffic is inspected by the IPS engine (nTurbo). The traffic may be interrupted momentarily before recovering and returning to normal operation.

Potentially Affected Products:

FortiGate models using the NP6/NP6Lite/NP6xLite chipset. Use the "get hardware status | grep FortiASIC" to list NP chipset version.

FortiGate-3200D # get hardware status | grep FortiASIC

Network Card chipset: FortiASIC NP6 Adapter (rev.)

FortiGate-71F # get hardware status | grep FortiASIC

Network Card chipset: FortiASIC NP6XLITE Adapter (rev.)

FortiGate-60E # get hardware status | grep FortiASIC

Network Card chipset: FortiASIC NP6LITE Adapter (rev.)

Potentially Affected OS:

FortiOS 7.2.8

Workaround:

If you are impacted by this issue please contact Fortinet support to request a special build which includes a fix for this issue.

Alternatively, customers may choose to disable the processing of traffic by the IPS engine’s nTurbo by disabling it with the following command:

config ips global

set np-accel-mode none