Re "Issues with Large Files" and "Recent Radio Downloads Not Playing".

[batguano999]

>The resultant file with a duration of 1800s 
>(30min) did play on the AGPtEK player, but durations of 1900s and more did 
>not play. That is an improvement on 14min
>

So you could probably download a m4a radio show that is not longer than 1800 seconds...
get_iplayer --force --mode=dashhigh --raw --type=radio url=<URL>
Then de-mux it...
ffmpeg -i foo.m4a -c copy foo.aac
Then re-mux it...
mp4creator -create=foo.aac NEW_foo.m4a

I do something like this all with the all de-mux/re-mux done in a --command.
get_iplayer --force --mode=dashhigh --raw --type=radio url=<URL> --command='WHATEVER'

Also with long shows I use a --command to split them into half hour segments and de-mux/re-mux them all.
The files play sequentially in my mp3 player.
After each half hour there is a "clunk" as the file changes.
Like an 8-track cart player back in the day.