Thanks Carl. I think you may be correct as the sea strainer is quite large and is directly connected by piping (not hose). It could be transmitting a force to the plastic valve which over time, could deform it. I recall
that there was some difficulty getting all the plumbing
in this area to seal when the boat was first launched in 2008, probably reaulting in some heavier torques being applied to these components. It does seem odd that there are repeated failures in this application where all the other Forespar valves are holding up fine.
Perhaps we can retrofit some hose or flexible mounts as you describe - will discuss with the builder