Cruise Control not working

I have the facelifted Exclusive Trim c3 from 2006 and my cruise-control controls are not located as seen in this topic. Instead they're on a separate stick just next to lights/blinkers stick on the left of the steering wheel as seen here:
The problem:
Every now and then cruise control does not work. I do the exact same thing every time and cruise control works whenever it wishes to. Hard to spot a patter in order to troubleshoot the issue. In the pdf manual I found for my c3 it says:

'This device is active at speeds above approx. 40 km/h (25 mph), in the higher gears only.' And indeed whenever it decides to work it works only on 4th and 5th gear, precisely over 40km/h so that's all fine.

I've noticed that if I stop the car and turn off the engine and start it again then I'm able to recover from this annoying error. But I simply can't do that all the time.

Any tips as to how to troubleshoot it? Does it have anything to do with the alternator's supply of power? The issue occurs regardless of whether or not I have the a/c, the lights, radio, charging phone on or off. Completely patternless, which is puzzling. I don't have a lexia sadly and I doubt anyone around has it.

soewhaty wrote:I don't have a lexia sadly and I doubt anyone around has it.

If you want to diagnose electronic faults on the C3, you will find lexia very useful once you get to grips with it. I suggest you purchase a lexia if you don't have one. Find a lexia clone here (ebay) and read up about it here, in this lexia topic.

The cruise control is all electronic and not mechanical other than the switch in your picture.

Thanks for the reply and sorry for posting initially in the wrong section!

You could try a new or replacement switch assembly. Its a bit of a guess, but it its giving trouble then changing it should show an immediate improvement.

The stalk (switch assembly) is used in other Citroen and Peugeot models and you can find them on ebay - here and is not too difficult to replace.