Rebuilding the desk
The old desk had wobbled for two years and I had fixed it with a folded coaster for most of them. This month I finally took it apart. The problem was never the legs; it was a single stripped screw in the back rail that let the whole frame rack a few millimetres under any weight.
I cut a new rail from a leftover shelf board, squared everything with a clamp and a level, and used proper bolts instead of the original screws. It is boring and it is solid. The coaster has been retired with honours.
Lesson, again: the thing that annoys you daily is usually one small fault, not a big one, and you can live with it far longer than you should.