Hello Jillo,
From your description the concern you have seems very unusual. I cannot recall anything similar, so it is really very difficult to fully appreciate the nature of the problem without a good visual reference, such as seeing it or a photo or actually inspecting it in the flesh.
If your caravan is still under the manufacturers warranty, you would be best to contact your dealer.
Unless someone else has actually had the same issue and resolved it, I think forum is going to struggle to diagnosing it. You might be better to arrange for caravan service company (a dealer or independent mobile workshop) to inspect and advise.