If it's uneven, the box may have become detached from the routed hole, and is no longer bonded to the core. My guess is that it is, but I could be wrong. To tell, take your thumb and push down on the box firmly... does the box go up and down? If it does, you'd better have the box taken out and replaced... not a job you're equipped for. If not, though... you could sand down the raised edge of the box until it's even, tape over the tab and grub screw holes, and trim close with a razor blade. Then laminate a small four oz patch over it, fair the edges, hotcoat, sand. Or hope it's still structurally sound, and just sand and hotcoat to make sure it's water tight.
Is it loose? If it is- then I could be a pain. If not- what ever these guys said would work just to make sure it does leak. If you have to replace the fin box- take it somewhere. I can't tell by the pic- but it looks like the glass on the bottom of the pic around the fin box is not structurally sound anymore. Lb crew pretty much just summed it up - if that's the case. If you put in your fin and can wiggle the fin- take it in
It looks like a serious stress fracture...looks like a knee or something of that nature hit on the inside of the fin. It'll temporarily hold...but it is eventually going to take on water and fail...seen a ton of them on both fcs and futures...not an expensive repair and should be back to you within a week.
