I've personally seen a few Nordics (37s and 42s) with moisture penetration into the salon top deck core. I've been told that those boats can frequently develop cracks at the aft end of the pilothouse bulkhead, where it forms a 90 deg angle at the forward end of the salon top boat deck (just beneath the aft pilothouse windows, perhaps a stress point?).
Once there is a crack there, it unfortunately allows ready access for water, which then wicks along the balsa core in the salon deck - and can saturate a large area. I've seen boats where that crack is repaired and looks good, but the much more expensive problem of moisture in the deck core was not addressed.
A moisture meter can be your best friend here.