Exactly as commenters predicted and I had hoped, Kershaw wrote back promptly Monday. They're sending new springs, and suggested Loc-Tite for the loose threaded insert.*
They say it could take up to ten days for the parts to arrive. Given that they're costing me exactly zero and will restore two knives I'm fond of and find very useful, that's a small thing indeed.
Other companies, pay heed -- it appears these guys have got that "customer service" thing figured out.
* Blue Loc-Tite -- and friends and geeks, do pay close attention to the grade/color of suggested Loc-Tite, as the hard-core red "cylindrical part locker" is forever unless you apply heat, while the remainder have varying degrees of hold/suitability to thread pitch and you do not want to use the wrong one!
4 months ago