The GUI and CLI of FortiGate units with NP6 processors may become unresponsive when the system is under heavy processing load because NP6 interrupts overload the CPUs preventing CPU cycles from being used for management tasks. You can resolve this issue by using the following command to dedicate CPU core 0 to management tasks.
config system npu
set dedicated-management-cpu enable
All management tasks are then processed by CPU 0. NP6 interrupts that would normally be handed by CPU 0 are added to CPU 1, resulting in CPU 1 processes more interrupts. The
dedicated-management-cpu option is disabled by default.