Kapusta

My experience with this style of seat clamp is that they can be frustrating to keep tightened if you don't pay attention to how the two serrated halves fit together.

When you go to tighten it initially, if the two halves are not perfectly seated together, they may snug up at first in that un-seated position, but as you rock the saddle back and forth over time (getting in and out of the saddle) it breaks loose, and finds that "seated" position. The problem is that the bolt is now a little loose, and your saddle starts wobbling.

What I do is this: tighten the bolt just enough to just keep the saddle from having any play in the position I want it. Then loosen the bolt just a hair and rock the saddle fore/aft. It should only move a tiny bit, because of the the serrated halves fit together. Then very slowly tighten it while continuing to wiggle the saddle fore/aft until there is no more play. Then go ahead and fully tighten it. This basically makes sure it is fully seated.

Since doing this, I have never had a seat clamp come lose in over 18 years, including one that had done so repeatedly before I figured this out.

Of course, if you tighten the crap out of your post enough times without it seated, you may have buggered the way they fit together.

Give it a try.