Thetford Aspire 2 paint flaking off

We have a Compass Casita 550, 3y 6months old. We have a problem with paint bubbling and flaking off the top of the Thetford cooker (strip where it joins the worktop and on the flat area behind the oven vent). Thetford have rejected any warranty claim as it is over 3 years old. Surely this is just poor manufacture and should be put right. Has anyone else had similar issues please?

Thanks Paul