If the boat is currently in cold Boston waters, it is possible that the heated air (with a higher relative humidity) is condensing on the colder panels and soaking in, thereby swelling the wood. You might try removing one panel, placing it in a relatively high location so that it will see the higher temperatures/lower relative humidity and see if it returns to a size that fits the location. If the test panel fits after drying for a few days, then you have your answer.
There aren't any hinges; all of the panels lift out.
I also just this evening realized that the panel outboard of the table is stuck too, but the ones directly beneath the table are easy to open.
SM 233 Iteration