my suggestion :
first find any ways were the water could get in . like tha anchor locker, lifeline stanchions, etc etc
than dry the boat out over the winter and than repeat the moisture detection .... through various intenrnet accounts I have learned NOT to trust any surveyors .... Some of them have no idea how to work the moisture meter, and they fiddle as long as it takes, if they get a boat which is over 15 years old to find something..... after all the moisture meter has to pay for itself....
Yes I am a little critical about surveyoos, still need to have the pleasure to meet a good one yet.
Thor