Last 3rd of LP has High Feq. Distortion

This absolutely sounds like an alignment problem and thats why it is happening at the end of the side. I think I know what your talking about. The proper term is sibilance. Its as if the S in the S words is dragged out and tizzy. Like the voice was poorly mic ed. This is typical of the cartridge being out of alignment or the cartridge is old and the stylus has warned causing an alignment issue. Also the stylus could have been unknowingly damaged. Even if it looks aligned twist the cart slightly towards the spindle and see what happens. If this doesn’t work pull the cart out a little on overhang. Then twist it slightly outwards. More than likely it will be the first adjustment that corrects it. If it doesn’t. Try every direction and don’t be afraid to really move it. . look at the stylus under a microscope. Try another cartridge as well. Even if the body looks aligned it may not be. The cantilever could be off. The first years of my analog endeavor I thought all the tracks on the inside of the record were like that....LOL!!!!! Records and tracks I thought were unlistenable no longer have any issues for many years. Proper set-up I find effects tracking far more than sound. You certainly get better sound with proper set-up but what you really get is dead quite tracking regardless of record condition or cleanliness. This sibilance you speak of certainly sounds like miss-tracking or an old or damaged stylus. Then again it could be the records, who knows right? I love classic pressings.