LG B7V OLED - Anyone know how to rollback the firmware?

[BigPest]

I've been having massive issues with my TV over the past month with HDMI ARC/CEC issues...it seems it's the TVs firmware could have caused recent issues as I've tried literally every fix to sort out this issue.
I've heard that you can access the service menu and rollback the firmware.

Does anyone know how to do this?

Thanks very much