Hi ash n,
I thing your truck may be abit short on hydraulic oil and may need topping up.
Mode 4 refer,s to the different take up of acceleration speeds your truck can achieve.
pressing button 1 will give you mode 1 button 2 will be faster still and so on. Its to enable you to make the truck suit the conditions you have to work in
The line contactor has a thermal resistor linked accross the main contact and is the to charge the capacitors in the power unit. It may be the thermal resistor that you have senced getting hot.
Depending on the age of this truck fault codes are shown on the dash display and may be shown as -02 or-56 you need to know what the codes mean to identifye the problem, a modern version of this truck will tell you in the dash exactly what the fault is, ie start switch closed.

Regards Titus