YES!
Before you pay for an engineer check the mains voltage inside your van.
I found my fridge sometimes clicked like this.
If the mains voltage is low, about 200V or so then it can't decide if it should to switch gas, tries to do so and then detects that it has mains electricity so switches back and repeats the process. ( the exact voltage range that causes this varies somewhere between 190 and 210 Volts. ) You are hearing the relay clinking.
I found out about this when the fridge only ticked when the heating is on. Many sites don't have thick enough cables so it is worse in winter.
Do check your mains cable as well. Some cheaper ones have iron instead of copper, this gives extra resistance so a bigger voltage drop.