The switch doesn't seem to work. It only goes on randomly

I would lean towards the headlamp relay. They are cheap and easy to replace. Try that and see.

Your problem seems to be from the keyboard. Even if it looks good if the keyboard tape is out of whack or some key is no longer working, it can happen that you say, so I change the keyboard.

if you have alot things on keychain ignition could be going bad. shake switch when it happens. sometimes remove weight from keys can stop it

the fork lift has several safety devices that will not allow it to start until everything is set
you in the seat , foot on the brake , transmission in neutral and hand brake on
it is designed so that you cannot start it from the side where if it starts it runs away uncontrolled
check for all operational safety switches

First I would get those brakes looked at. There are generally little wire wear switches in the brake pads. When they wear the wire off, it trips the computer something is wrong. Heavens can only guess what else it does in the ECU mind. So fix that first and then see if problem goes away.

Check the vacume pipes under the viper shield behind the engine.

Make sure that the input switch is not getting stuck

It seems that the car player front panel is having some errors , possible that it triggers the FF until you tap on the panel . So now run a DVD and see if this goes on FF, is so tap the front panel or the dash board. If the fault clears then you need to remove the in- car fittings and check out the control panel of the set. clean all contacts , switches and connectors.

change the battery

i guess the battery doesn have enough power to start all the units u mentioned.....u have the problem with ur battery.......thats it!!!!!