Some of it looks like usual wear, but those cracks and missings bits are scary. My immediate thought was structural and too much bending in that part. As this is mostly above the "working part" of the foil, I would have had a go at reinforcing it rather than risking a break. Hollow foils with gelcoat sounds like an oxymoron, but I know as good as nothing about Bimare products.

To "fix" it I would have sanded and put on some glass. When hard I would have added epoxy thickened with microfibers and collodial silica, put on a very thin layer of plastic film and put the foil in the "down" position in the rudderhead. Then clean up around the rudderhead section. Perfect fit and more durable than gelcoat.