This scenario seems to occur after local repainting. More than once I have had to decide if the coat of paint has been applied where it shouldn't be. Often the maintenance manuals are of no help.
I remember being given a hard time by one chief engineer for removing paint from a repainted Dauphin tailboom at the point where the tail gearbox mounting tripod met the duct inner surfaces.
This subject should be highlighted in the CAP 747 appendix dealing with aircraft repainting.
It seems very sad that lives may have been lost due to a well known and common problem.