Hi Mick
I had a S5 Vendee for 4 years with no problems. There was a batch where allegedly the ABS panels had been fitted in a stressed state causing premature cracking and water ingress. As they all had 6 year water ingress guarantees , in theory any problems should have been resolved by now.
No matter which model or make of caravan you buy make sure a t horough damp test is done first.