I also have a L440 2006 model (hull #72) but have not had that problem. I am not aware of the bearing/bushing material that Lagoon
uses but my previous cat, a 55ft Schionning had nylon bushings that developed the stiff rudder
problem due to uptake of water
in the nylon. I am told that some nylon variants will do this and "grow". The solution was to drop the rudders out and hone out the nylon bushings while still in place, sufficient to provide some clearance to allow the rudder
shafts to turn. You may be lucky and be able to simply use sand paper to do this. You may get the centerlines slightly off but the nylon will soon conform again when in use. It is pretty easy really once you drop the rudders out and clean up the shafts at the same time.