Hi Ted, it could be several things and it would help to have a picture of the works and I am thinking especially the escapement. Also did you check and or install any bushings???? possible a bent pivot??? the reason I am thinking about the escapement is because I would also want to look at the angles of impulse and the locking faces between the escape wheel and verge pallets. Anyway like I said it could be many things and with pics or a little brainstorming I am sure we can figure this out. check and see if any of the past posts would have info for your situation, sometimes they can inspire ideas for you. 
Have a great thanksgiving, William
