One of my favorite briars, an old no-name pipe, suddenly won't keeping burning. Where I would get a nice 15-20 minute smoke now I am constantly relighting. I have very carefully cleaned the stem with alcohol dampened pipe cleaners and made sure that the shank is nice an unobstructed. It's not the tobacco because It happens with the three I smoke, and it isn't me because my other two pipes are smoking well. Help.