Q: I have 150dc 1969 Gibson the last fret on high E must be too high or next one is too low but it creates the same note unless I raise action,so I avoid it but tempted to bang it down or sand/file it would be the last fret. I dont think I could screw things up any suggestions it plays great otherwise.
A: The first fret is the one at the peghead end of the fingerboard. The last fret is the one at the end closest to the bridge. I am going to guess that what you are talking about is that the last two frets play the same note. This is because the last fret is too high. But why is it too high? It could have come loose and raised out of the slot. Or, the neck could have bent forward, making a slight U shape, then the bridge was lowered until the string fretted out on the last fret.
Your talk of banging it down makes me think you might be able to see that it has raised out of the slot. The metal memory of the fret outlasts the grip of the slot on the fret. When you drive a fret you pre-bend the wire to a greater arc then that of the fingerboard. Then you tap in both ends and then drive in the middle by hammering along the length of the fret. Hammering frets is a gentle art. If the metal memory and the grip of the wood on the fret are working together the fret will hold forever. But if the fret is flatter than the arc of the fingerboard and the fret end is only being held in place by the grip of the wood against the fret tang, over the years the wood will shrink and let the fret end rise. This would produce your symptom of only effecting the high E string. Banging on the fret end is like hammering on the end of a diving board. The fret must be pulled out, re-bent and re-driven.
The other explanation is that your neck has warped forward over the years. Wood changes shape every time the weather changes. If the neck warps backward it will come back with the next weather change. If it warps forward it has between 100 and 200 pounds of string tension (depending on your choice of strings) holding it there. As the neck bends into a U shape the action gets higher from the nut to the 7th fret. Every music store in the world knows, if the action is too high, you lower the bridge. But, you can only lower the bridge until the strings buzz on the top frets.
The end of the story is that the action of a guitar is a function involving the straightness of the neck, the levelness of the fret tops, the roundness of the fret tops and the height of the nut and the height of the bridge. If you change one item of the function all the others must be readjusted. Filing one fret is never the solution to a bad action. Music stores do not advertise the fact that they don't have a luthier on staff. Any music store that you go into will run your bridge up and down and twist your truss rod and call it an action set. A real action set will start with fret leveling and will cost at least $65. A 1969 guitar is probably due to have some worn frets, if not all the frets, replaced. Guitars need adjustment every few years. They need major surgery every 20 years or so. It sounds like your guitar is overdue for a trip to a luthier.