Try an OLD utility called FixDisk. You can read and re-read the bad track by clicking a button until the hex values for the track look "okay" (i.e. the progression of numbers matches the others you can see rather than garbage). Then you can format just the one track and rewrite the good (stored) values. It is the only utility I ever tried with floppies that ever really fixed intermittent read errors where you KNOW that every now and again there is a good read.
