As I asked in your other topic iPod classic aiff format metadata - recipe for problems? - #6 by Gale_Andrews
If you export a single AIFF from a whole track, with all metadata fields completed, do Amadeus and Peak have the same problem?
That is, if you save a single AIFF created in Audacity in Amadeus and Peak, do they empty the metadata? But they don’t do that with AIFF’s created by iTunes?
Have you tried iPod connected to the computer, to rule out battery power as the reason it will not play Audacity-created AIFF’s that contain metadata?

Aiff with metadata, not in track order and does not play properly.
Please generate a tone or record something in Audacity then give us steps 1, 2, 3 to reproduce this
problem. Don’t use AIFF files already created by iTunes because we know Audacity modifies iTunes NORM and PGAP.
Tell us exactly how you are splitting the tracks using Export Multiple and exactly what you are typing into Metadata Editor. Tell us exactly in what way the exported files are “not in track order”.
Better still, please upload some AIFF files produced by Audacity Export Multiple from a tone or a recording to a web server so that someone who has iPod on Mac can try them.

Aiff works with iTunes and on iPad .
Are you talking about AIFF files written by iTunes, including those converted by iTunes from WAV or AIFF files produced by Audacity?
If so, isn’t that a useful workaround to the problem?
Gale