Jim, two things come to mind.
First, when you sail, do you take up the extra tension on the centerboard halyard? If you do not, the water will spin your centerboard Halyard and so when you do pull the center board up, the line has twists in it and it binds in the halyard tube.Second thought, the centerboard has a stainless "U" shaped band that connects the halyard to the center board. That could be bent. Some boats have small shackles that connects the halyard to the centerboard. If the shackle enters the halyard tube, it can jamb. In the Great Lakes area, zebra mussels can fill the centerboard trunk or grow on the centerboard to make it tight.In my area we have a .... I am not sure what to call it, a jelly looking blob that grows in our lake. If you beach the boat , it could be mud or rocks stuck in the housing.The last and worst situation, if you have damaged the leading edge of the centerboard. It is taking on water and expanding and is now jambing in the centerboard trunk.I hope this gives you places to look. Let us know if you have further info as to what has caused the problem. Also let us know what you find that caused it.Jim would you please edit your post and delete your link. The link is a pain to deal with.r.w.landau