First, have you looked at the metadata stuff and made sure there's no confusion there? Different artist, different album ...
If all is good with the files, try a hard reset. With the power on, remove the battery for at least 30 seconds. Then check again.
If you still have a problem try deleting ALL .dat files on the media card in the music folders. If you have encryption enabled you may also have .dat.rem -- delete those too.
If you have the podcast app you will have some .dat (and maybe .dat.rem) files in the podcasts folder. I don't know what problems with the podcast app if those are deleted, so maybe hold off on deleting those if you don't have too.
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