"File format not supported" randomly appears

I get this with everything. I use the ogg-vorbis file type for my music that I ripped from CDs. Every song is 44100 Hz sample rate,140 kbps bit rate, downmixed to mono.

I can grab 30 folders and copy them at once or carefully copy one folder at a time. It just doesn’t matter how I get music on it
I just know that I will stick to my Sansa Clip (not clip+) with it’s slowly failing battery until this issue is resolved