You could try burning a DVD-A disc of the show with DVD-Audiofile and see if there are gaps on the original 24 bit files. DVD-Audiofile doesn't add gaps between tracks. Also you could look at the files with CD-Wav editor (free). You can look at the wavs and see if there is any silence at the beginning or end of a file.

I've never used Audacity for converting from 24 > 16 bit. I have only used Wavelab, and I've never burned the files to audio CD. It could be you had some settings wrong in Audacity? Also you could decode the 16 bit files to wav and see if there are any other problems with the len check, like non-canonical header errors. These will show up in the middle column of the len check as an "h"

Just thought of this: you said you used a FLAC plugin for Audacity to do the conversion from 24 > 16. That plugin could be the problem right there. I would decode the original 24 bit FLACs to wav, then load the wavs into Audacity, then dither and convert to 16 bit wav. Then load the wavs into Trader's Little Helper to fix any errors. Finally, burn to audio CD. Hope that helps.