Howdy, good question and brings up a good point, It would benefit us if we checked out the movement first and try identifying all problem point beforehand, just a thought. 
I would only be guessing but are the front and back plates square with each other???? are there any pinions worn on the fly???? do you have a depthing tool???? am I going crazy??? 😯 or getting old???? 😥 is the fly arbor bent???? or if you look down thru the movement are the arbors parallel with each other??? some quick things to check, let us know what else you may find…God bless, William
