there are 2 sets of lazzarete lockers- first in the deck and second on transom step- i have found another cause of water into the deck lockers is if you have a lot of water running down the deck- say like a heavy rain storm, the water exits the deck at the end of the toe rail , which is just at the rear edge of the deck locker hatch- i found that water was draining in through this lid gap and the drain is unable to cope- it overflows and there is only a single drain tube for the entire lid drain. I have added a small "P' shaped rubber gasket to seal this gap on this low side- i now have dry lockers!
The other obvious one is on the transom step lockers- i added latches as without these in a big following sea water can actuallly lift the lids and water pours in! I can post some pictures next week if you like.