I think I'd be looking at leaking rail stanchion fixings. I don't know what you have on a B41(2003), but if it's the same system as on a 36(2002), then rail stanchion leaks are something of a problem. Particularly if like my 36 yours should happen to be an ex charter boat where charterers would almost always pull themselves onboard using the rails or stanchions rather than the mast shrouds. In consequence the excessive strain this places on the stanchion base fixings results in fresh water leakage which can be particularly noticeable over the winter months when your boat is tied up in a marina, or is on shore out of commission in a cradle. Wobbly stanchions are a dead giveaway for this problem, but just because they don't only doesn't mean that the problem does not exist. Then you have to figure out how it gets into the fridge. On my boat the hatch for the fridge is set into the counter top close to the galley sink, and the hatch does not have a watertight seal. So any leakage or condensation dropping onto that counter top is likely to end up inside the fridge.
The next thing to watch for during the winter period is condensation. Staying overnight recently on one of the coldest nights of the winter resulted in a huge amount of condensation being noticed by the following morning. Some of this will undoubtedly have been from moisture from my own breath, but will also have been as a result of moist air entering the cabin during the relatively warm sunny afternoon from the previous day and then condensing out on the cold areas around ports, skylights and hatches.
