Can't play full audio files
Since this has been open for a week, I decided to post my workaround and the other details I found as an answer.  Mods, please don't close other similar questions, because this is not an actual answer, just a hotfix that might help someone later.

Just wanted to update: 1) Found a workaround using the VLC Player (still in beta) to open the files. 2) After going back to google basics and figuring out a better way to ask, it looks like it might be an issue with variable bit rates; unfortunately, when I downloaded an app to fix that, it came back telling me that based on the file tags, it thinks they're constant bit rate and not variable. I'm way outside my area of focus on this one, but TL;DR is that the file on the device is not corrupt, as I can get it to play with the VLC app.