[iTunes] Autofill and the Shuffle; I just don't get it.

[i.am.list.boy at gmail.com]

A few years ago, bought my father a first generation Shuffle, and  
whenever he visits we bang our heads against the wall trying to get  
Autofill to work. Seemed like instead of automatically syncing, we  
had to manually drag songs/podcasts onto the unit.

Just bought my mother one, and having a different but similarly  
maddening issue;
I set up a playlist with 5 podcasts. I mount her (2nd gen, 1 GB)  
Shuffle, and direct it to "Autofill" from the playlist.

Only 3 of the 5 podcasts sync'ed. Combined, the 3 were less than 100 mb.

And no, they weren't video podcasts.

I can't find anything on Apple or Google that clarifies things for me.
Can anyone here help?