Okay, another problem encountered..
Following on from my recent post - Recommend an AVI Editing program
Whilst using ConvertX on these .avi files, it identifies that some of them have multiple audio channels (all of a different bit-rate, I think).
Please see the attached screen print, outlining the problem.
I've been told (by ConvertX Forum) that this is most likely to have been poor initial coding.
Sooooooo, now looking for a nice easy-to-use (FREE, if possible) audio repair program that will help in this regard.