problem with thorens 320mkIII

plays flawlessly until about last track- one channel starts distorting, at which time the tonearm starts skipping and staying in the same place. Can someone help me- Thorens have a peculiar setup sequence
Sounds like the tonearm needs to turned toward the center of the record. Loosen the hold down screws just enough to twist the arm until it reaches the end of the record. Either that or something is binding underneath.
Look to see if the bottom of the tonearm is making contact with the top of the arm lift as it travels to the inner grooves. If so, there is a set screw that will lower the whole arm lift. An easy test for this may be to put an old record under the turntable mat thus raising the playing angle of the arm.