I believe the SKB triggers, at least the ones I have owned are mechanical not inertia. It is unlikely that fouling will inable a mechanical trigger without some other issue. inertia triggers, ( Browning superposed et al) can be touchy. Check your trigger pulls with a gauge, there can be a vast difference in pull pressure. I have seen triggers from 2.5#'s to 11#'s!!!, First pull should be around 4# to release, second trigger should be about 4.5#'s to eliminate doubling in a mechanical trigger, and recoil doubling in an inertia gun. many times doubling is a user error, in which the shooter,usually using gloves, doesn't fully release the trigger upon firing the first shot, in this situation any slight rearward pressure on certain triggers will allow recoil to fire the second shot. If your gun fired both simultaneously, there is an issue with your barrel selector, either it was in no mans land,not fully to left or right, or it is not functioning properly due to wear. Third possibility is a worn sear. In any case SKB especially of the early vintage,the Ithaca guns, and shortly after have an excellent reputation and were ahead of their time. It can be fixed, and is well worth it. Any gun of it's class new will cost several thousand more. today.