Managed Fortiswitches choose primary

Hi all,

I have a setup consisting of 2 FG100F in HA mode and pair of FS124F connected to both chasis in HA as follows:

FS SW01 port24 to FG primary port18, port23 to FG secondary port17

FS SW02 port24 to FG primary port17, port23 to FG secondary port28

SW01 and SW02 are interconnected port22 to port22.

Server load has redundant interfaces connected to both switches to their respective ports.

Ok, everything works fine, if one switch fails everything is still up.

My question is: how to "force" SW01 to become primary again after some sort of temporary failure?

Many thanks and please dont ask me why customer didnt went to MCLAG supported switches.