Terry, let me add my kudos to those of bord for your excellent efforts at preserving and restoring Welles' audio works.
Thinking about variation you find in results from one episode to another of The Lives of Harry Lime (or The Adventures of Harry Lime, as they were known in the United States) -- and again, if you attempted a similar restoration of The Magnificent Ambersons -- I am prompted to recall the differences, some of which were initiated by Welles, in the area of Radio Transmission, transcriptions, Spoken Word recordings, etc., over a period of nearly twenty years.
In the decade of the 1930's, as you indicate, most recordings, if made at all, were on coated glass discs. In America, these "air checks" were made at the order of the FCC, and once filed, were often forgotten, just as frequently poorly stored. Each disc contained only part of the program's airtime. It is the luck of the draw, how well recorded, how often played, how kindly treated in the passing of time the quality of a given program might be.
By 1951. the technology was much more as we know it today. Many radio stations still used transmission discs, but they were large affairs, much more faithful in sound quality. By that time, magnetic tape, 45 r.p.m.'s, and 33 long play records were in the field.
In the case of the Harry Lime stories and other Harry Alan Towers' extravaganzas with Welles, unlike trans-national exchanges of the past which had to depend upon short wave transmission, the programs were technically designed for Worldwide distribution. Towers' Harry Lime work, though often shabby in terms of art or even state of the art, were among the first of these. They benefited from the good reviews and mass commercial audience reception THE THIRD MAN had received. [One of the first .45 r.p.m.'s which I purchased to play on our new RCA radio-phono console was the zither music of Anton Karas for Carol Reed's film; it was an international sensation, no matter what some of the producers had thought of it at the time.] And so, though radio sound had generally improved greatly, differences in reproduction, equipment, and use of given transcriptions in various English speaking countries may explain some of your difficulties in bringing your online work up to the snuff you desire.
Please, press on.