I had a 1996 Hunter 280, and the hull / keel joint was never an issue.
I had the 5-foot deep draft keel. Do you have that or the shoal keel?
Do you have a crack at the hull / keel joint?
Ever ground the boat?
I can’t imagine the keel can move without cracking the joint.
The bilge is very shallow on that boat, not much of a keel stub if I remember correctly.
Greg