Damp picked up on service

I picked up my 2014 Buccaneer Schooner back in July 2023 and bought it based on a positive looking service which was carried out by the dealer - damp readings were between 9 and 11 per cent around the whole caravan. 

Yesterday the caravan was serviced and the damp readings had increased significantly based on the damp inspection 10 months ago. They are now as high as 63%!

This is my first caravan so I’m not an expert - but the company servicing the caravan advised that it is virtually impossible that the damp can get this much worse in 10 months - especially as he carried out the inspection on a warm day. His professional opinion is that the report from 2020 was doctored and inaccurate, probably to not put me off from buying the caravan.

I want to try and take this further now - has anyone had any experience with this and where can I go with this? The caravan was bought from a dealer in Manchester rather than privately.