Had quality problems also with fin and fin boxes,on my race board Airush Sector purchased at the beggining of summer...again Repaired Myself.
Everyday i hate more this industry and feel they're scamming us with china cheappy quality products (specially directional boards) supossed to be designed to last.
Same problem here, the fins of the sector, but was offered by Airush to get a quote and have it repaired, The fins were cutting into the finboxes and the bottom of the board, problem is that the sharp edges were cutting ito the board, as these were left too long and by tighthening the screws from the top ...the fins were drawn into the board, once the pressure came on them while riding the board they digged in into the board and finboxes.
Can you tell me how you repaired it? maybe pictures?