Howdy Phil, try this, first check the balance to see if everything is looking right, if nothing seems obvious take out the balance and see if you can move the pallet fork from side to side with a very light touch of a toothpick or pegwood, if nothing happens then take out the pallet fork (make sure you let down the mainspring 
) wind it a turn or 2 and see if you are getting any movement at the escape wheel (make sure you have oiled the movement ) Basically you are trying to isolate the problem area into sections, ie, train, escapement, balance….it is possible the problem will become (more) clear, let us know how it goes, William
