Like many boats, #357 had this same issue before I purchased her. The PO had Waterline Systems address this by using a top side G10 stiffener plate that spread the load out. Over the years however, there was water infiltration from a path formed between the top and bottom skins in that area in your picture which has no core. This path caused wet core near a couple of these stanchion bases which I later repaired by recoring from the top, then applying AwlGrip & Griptex. This improved the stability of the stanchions. In your case, I would be curious if there was any wet core in that area or delamination, which you might detect with a moisture meter, hammer and maybe a core drill sample from the bottom side. If it turns out to be sound and dry, you might be able to restore some structure with a G10 plate glassed onto the bottom skin.
