If they cannot be recovered using these suggested tools, then you will have to try from an older backup if you have one, or rip again from the original source if possible. But the tags have nothing to do with the audio portion of the files..
Have you tried the suggested tool MP3Val? This has fixed many bad files that I had over the years.
Ultimately I have to pull out my original CDs to correct a few unrecoverable file errors. But in my case this made sense as I now only use lossless, whereas long ago when storage was at a premium, many of my rips were only at 192kHZ or 256kHz mp3.