Sonicake Pocket Master - NAM uploads disappear

Anyone else run into this with a Sonicake Pocket Master? I upload a NAM file using their manager software, it seems to upload OK, says it succeeded, and the file name shows up in the slot. But if I try to find it in the clone list on the box itself, it's not there. And if I flip to another page and back in the manager, the slot shows empty again.

I've also found at least one that loads and sticks, but doesn't pass any audio when selected. Yet, some NAM files will upload and work just fine. These are all downloaded from tone3000.com I assume there's some property in the files that's not compatible, but is there any way to tell? Trial and error kind of sucks, especially when more don't work than do.