Newf, it is possible the lug is loose now, it is secured when originally made with a screw from the top of the barrels before the top rib was laid. The bump in the lower rib is an indication that the lug has shifted forward slightly. Mark the lugs position and tap it lightly towards the rear, if it moves the solder joint holding it to the barrels has failed and it needs to be reset

I learn something every day, and a lot of times it's that what I learned the day before was wrong