I tend to agree with Roger that the caravan industry has been aware for over 10 years of the shortcomings of using ABS panels on caravans as they do not like stress as per
https://plasticextrusiontech.net/resources/what-is-abs-material/ which is why there is only a 1 year warranty on panels.
ABS or Acrylonitrile butadiene styrene is a common thermoplastic polymer typically used for injection moulding applications. This engineering plastic is popular due to its low production cost and the ease with which the material is machined by plastic manufacturers.
The crack is located where the front panel joins the roof and as you can see from the photo, the crack is just over an inch long and is located where there is a slight bend in the moulding. Not sure why they think it could be due to the reasons offered by the dealer.
In hindsight as said the caravan was thoroughly inspected in Oct and no issue. Next trip after the service was the a 90 mile round trip to a CL mainly on M5 and reasonably decent roads, however when we delivered the caravan to the dealer the main road to the dealership was closed and we had to use back roads which were very winding and bumpy.
Anyone who has travelled to Brean may be aware of these back roads. We followed the diversion signs as set up by the council and had to travel well below 30mph. Possibility the crack was waiting for us to travel on just such a road to manifest itself.
Either way a crack costing over £9000 to repair should not happen on a caravan that was just over 4 years old taking into consideration the original price paid the panel is certainly not durable under CRA 2015!