Originally Posted by Moe Zhoost

Bingo! It's hard to figure out what's what in that photo. Could you strip off the stuff that is irrelevant and take additional pictures?

Oh, I took another look. It appears that you added all of that junk to serve as spacers between the top of the seat tube and the bottom of that trailer hitch you have clamped onto the post. My bet is that you have a crack in your post clamp. It's small enough so it is not apparent when released, yet opens up slightly when clamped so that it's less than functional. A new clamp will probably do the trick. Also, we routinely grease seatposts before installation so that they don't corrode and stick in the tube. This grease does not affect positive clamping if the clamp is good.