It wasn't so much the SQ as the mix, they'd managed to leave one channel of the mix out at some points!
This from the Discogs debate at the time
" The problem with the reissue - on Side 1 - is only one side of the stereo image (the left channel of the original recording) has been pressed on to both channels of the record. The result is that when the first saxophone solos on the reissue (right channel of the original issue) you are actually only hearing the reverb of this instrument, hence the ‘recessed sound’. When the second sax solos on the reissue the signal is much stronger (albeit ‘drier’ than in the original, without reverb) as you are hearing the channel to which it was originally panned.... this problem only affects Side 1 of the reissue - Side 2 has the correct stereo image.
Its difficult to understand how such a glaring mistake can get through a professional mastering stage, and then not be picked up on by a record label before manufacturing - surely listening to a test pressing would have made it obvious that there had been a mistake?
I wonder if maybe the original master tape for Side 1 of the album is damaged, and so a decision was made to go ahead and press using only one channel, "