dave: I had the same problem with one of my locks,what is really happening is the powder when fired is getting under the frizzen area.
A fast fix is to apply a little glass bedding to the lock area were it meets the stock(under the frizzen powder pan) there is a ridge on the lock just above the coil spring and wre the frizzen screw is that the area were the burnt powder is getting under the lock.
J@B weld can be used not hard ,easy fix all you have to do is apply a small amount of expoy between the lock and wood,but remember to apply a coat of wax,or even pam cooking spray to all metal parts as a release agent,so once the expoy cures the lock will remove from the stock.Iam in n.c. would be glad in 2 weeks send you a few pictures when I get bach home were to apply the epoxy and all cleaning problem with the lock will be gone.