Inspection of my long neglected Viele revealed that the liner had traveled almost to the opposite end of the tang. Luckily, my C42 is the upgraded model that features an eccentric pivot pin. IIRC, the eccentric pivot pin was designed by the Spydercrew to tune the fit of the lock in final assembly. Back then, production tolerances were tight but not close enough to guarantee perfect lock-up in every knife. A side-effect is that the end-line user, i.e. me, can tweak the lock after it’s worn. You can move the entire blade a little closer to the liner to improve lockup. It’s also possible to move the blade away from the lock, if you want to.
I took off the clip to reveal the pivot pin which I unscrewed about ¾ before I pushed it through to the bolster-side of the handle. Turning the pivot assembly two slight turns in the right direction, and pushing it back in the handle, was all that was needed to start the liner right at the start of the tang again. This process took me about 10 minutes. The Viele also needed a bit of sharpening to be shaving sharp again.