Player skips over some songs

MP3 files are not a totally homogeneous group. You have different bitrates, and different codecs that output MP3s, let alone all the MPCs and the likes. You should check what your player's recommended bitrate is, and try to find what is common with the MP3s it can't play. Maybe you get them from the same source.

If you rip a cd, and output it to MP3 files, my bet is that either all or none will work, there is no randomness here.

The only other option is that the files got corrupted somehow, and the player can't read them.

Good luck