Man, that story really gets me because it's such a sneaky problem. You do the same thing for years, it looks right, it feels right, and then somebody points out a small noise and it unravels everything. I totally get that sinking feeling when you check your own kitchen and realize the customer was right the whole time. It's also kind of wild that a tiny bit of play on the non-captive side makes that big a difference over six months. I bet a lot of people never catch it because the slides still work fine, they just get loud and gritty sounding. Good on you for actually listening to her instead of blaming the hardware like most folks would. That 1/8 inch shim trick sounds like something worth remembering.

Ha! Exactly, @grace_perry44 always the thing you least expect. It got me one time after I spent a week changing every other part, turned out to be the dumb little sensor that cost less than a coffee. Shoulda checked that first, but hindsight's a real jerk sometimes.