Centre board release problem

my centre board appears to be stuck in the casing. It won't lower into deployed position.
My CC19 068 has been on the trailer from before I bought it last August from the previous owner. I have not been able to inspect the centre board with the boat on the trailer. Only after I had the boat lifted into the water last week and released the halyard, I noticed that the board does not move at all, trapped in the casing. Could this be caused by marine growth inside the casing, accumulated there during a long period in the water, before I bought the boat?
My idea would be to have the boat lifted on to a stand where I can access the centre board and casing from below and use a steel blade (saw?) to clear the space between case and board. Would this be the only option?
Any suggestions on how to release the board are welcome!
My CC19 068 has been on the trailer from before I bought it last August from the previous owner. I have not been able to inspect the centre board with the boat on the trailer. Only after I had the boat lifted into the water last week and released the halyard, I noticed that the board does not move at all, trapped in the casing. Could this be caused by marine growth inside the casing, accumulated there during a long period in the water, before I bought the boat?
My idea would be to have the boat lifted on to a stand where I can access the centre board and casing from below and use a steel blade (saw?) to clear the space between case and board. Would this be the only option?
Any suggestions on how to release the board are welcome!