Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?
The water ingress would not be into the pressure vessel itself, for obvious reasons, so it must be either into volumes that are exposed to vacuum in orbit, lying between the pressure vessel and the outer casing, or into empty tanks with an open path between them and the water.
The designers would surely have known about the first case and allowed for it, so it must be the second case. One possible path for water to enter would be through a Draco rocket nozzle, past an open or partly open injector and valve and into one of the hypergolic propellant tanks.
If it had only happened once, I would think that it was an error in procedures where somebody forgot to close the valve after the tank emptied, but since it appears to have happened several times, I'm guessing that it might be a design or manufacturing flaw with the valves, where they do not fully close as commanded when there is significant water pressure on the downstream side of the valve.