reel repair is tough for a shop. Every reel is different in every little minute part internally. If the drag isn't working properly one tip to make sure you do is take all the drag tension off your reels after you're done using them. Think of keeping the brakes pressed down on your car while it's parked. Could make things stick and then not work over time. More often than not a bad drag on cork is because the cork has worn out or worn unevenly over time. A little bit of annual maintenance goes a long way. Take the reel apart and put some gun oil on the moving parts and treat the cork with something like some neats foot oil.
But as stated before, check with the manufacturer. They may have a warranty or some better advice on the specifics of fixing the reel.