I had a survey (didn't need one, but had one anyway). In any case centerboard was working fine when I bought the boat, during survey and opened and closed quite welll during trial sail. Survey predated the bottom paint work by precisely 3 days).
CB pennants are pretty much brand new, were recently replaced by PO (hence the ton of 5200 on cb trunk lid, PO liked things very firmly attached). I don't think they have to do anything with this issue, though.
I am not sure what the rest of your answer means, to be honest. I am looking for other ideas to solve the problem - if you have any, they would be appreciated. If you do not - thanks for your time