I was watching my TR47 rip of a ANH with my surround sound system and my PC, and realised that the audio also goes from dodgy to better in regards to quality. So in this case at least it seems this audio issue may have been there before or at least since the 93 LDs. Can't speak for the 97 SE editions, but it is my opinion that even then the quality of the better audio clips wasn't ever good enough until now to notice the difference. Maybe not.
In regards to the other audio glitches that's plain and simply Lucasfilm fuck ups, or so to speak.
RATLSNAKE
btw, for those who disagreed with my earlier comments in regards to the Lowry digital cleanup process, they did not have access to the original negatives, but rather negatives made by ILM after they cleaned them up themselves first, and made the color corrections, then transferred back to film and gave it to Lowry. he then made the comment that some scenes in ANH were so bad that their algorithm thought the dust and dirt was actually part of the picture. lol This is taken straight from My Lowry himself in a recent interview I read online the other day. I can't remember which site but it was one of the major American news websites.