An interesting weekend.
MY06 3.0RB wagon, reversing out of a parking spot... clunk!
Drove home very quietly, listening for noises (it was mechanical weight - not a trivial / trim sound)...
Took it over to the mechanic this morning, with no weight load we immediately saw the shock/coil assembly flopping around in the suspension tower.
The shock itself was in completely workable condition, no split, leaks etc. Only the top threaded shaft had sheared off, right up against the top nut (still captive under the rubber cap).
This suggests the factory at Subaru may have overtightened the top nut but that's yet to be determined!
I'm sending the parts back to Subaru later today for them to assess, as i believe the shock is still serviceable, and only the mounting failed due to an assembly error.
Hoping for a replacement shock, or at the very least a significant discount on the replacement part cost.
Wish me luck.