After we had our shell spray foamed by an established firm I carefully inspected and found quite a few hard to reach places where the foam hadn't quite penetrated fully, unavoidable really as the spray is directional. I finished the job by injecting aerosol foam into tiny cavities, took nearly a fortnight of re-inspecting to finish but even then a year or so later I found one tiny spot behind the bathroom lining that dripped slightly in very cold weather, A quick squirt with the aerosol sorted it.
I suspect some minor drips are very common on boats, usually concealed behind lining.
ETA: You can get condensation on foam, in very cold weather we had it forming on 1.5" of foam on the underside of the front deck, caused by cold air trapped in the well deck maybe? Fitting a cratch cover cured it (by reducing the temperature differential I guess)