Bizarre problem regarding albums being recognized

This issue won't be easy to explain, so thank you in advance for reading. Anyways, I've been setting up a new mp3 player with some music. Earlier today I had 65 albums on it, all working as expected, being in their proper folders in the albums section of the menu. Then I brought it up to 100 albums. Still plenty of hard drive space btw. Now, going to the albums section says I only have 70 albums, with the songs from the other 30 being collectively dumped in an "unknown" category. The crazy thing is that the albums that got sent to uncagegorized purgatory are a mix of the new ones I added and the old ones which were working fine earlier. So I know it's not a file formatting issue, the device was able to recognize that same folder as an album already.

So I did a quick experiment, and took four of the working albums off the sd card temporarily to see if it would reawaken some of the other albums. When I did that, it showed 71 albums. So removing four albums revived five different albums. I'm at a loss. The files of the working and not working albums appear to be set up exactly the same (same downloading source too), and besides, those folders were already working earlier. Any ideas?