Strange ticking noise

I have noticed recently that every so often we get a strange clicking/ticking sound which seems to be coming from either behind the cooker or sink on a 2014 Warwick Duo.
It seems to happen whenever there is some movement in the van such as when we first step in and it lasts for around 30 seconds regardless of whether or not we keep perfectly still. 
Obviously its a long shot but I was wondering if anyone else has experience of this before I start removing appliances?

There is a relay connected to a float switch in the freshwater tank, which switches off power to the filler point when tank is full. Movement in van, water sloshes and float intermittently telling relay, full, so it switches. Could be that?

If you have the Truma/Whale water filler , then read this thread which explains it....

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