All fixed! The problem was with the K1 relay.
Thank you for your help, Cheek!

Thank you. I'll try that.

Definetly. A poor battery creates issues. So stepping on the inner pedal does not start up the steer motor? I would check to see if you have power and ground at the solonoid. If so, change it. If not, trace what feed you are missing.

Can the battery cause that sort of a behaviuor?

Replaced all three - nothing changed.

Anytime I come across these kind of issues i always start with replacing all three switches. BRK 1, BRK2, and STS1. A slight voltage drop across these switches can cause many problems.

Thank you for the prompt reply. What actually happening is that the display lights up with the turn of the key and when I step on the floor plate (not the driving one, but the main floor plate) the relay clicks and display shows the mode of the fork (I can change the mode on the display) but nothing else is going on: pump does not kick in, neither strobe light or horn is working. When at last it starts up (after an unknown number of step ons and offs) it works as a charm: fork works fine, strobe and horn are ok, I step on the drive foot plate and it drives no problems. So I don't think the brakes need bleeding in this case as the motor switch engages every time I press on the foot/drive plate but it does not lead to anything until the unit starts up.

Is the slave cylinder contacting the motor switch each and every time? Perhaps you need to bleed the brakes.