Uhh yeah, I understand all of that (hence the last paragraph). I just figured these are small enough to actually fix (hence why I didn't say anything like "you need to redo all of this"). Or, in the case of Bernard, maybe I was wrong about him being born/raised in the US. Some of the issues may even be editing errors (noise removal gone awry or mistakes with splicing?) and may be fixable more easily if the raw recordings are still saved.
FWIW most of the voices are decent impressions of the original voices and good in their own right. Many of them you have to compare one-after-the-other to tell the difference (for instance the original Hoagie voice is more John Goodman-y--as in more gravelly yet booming--although I think the RotT voice is perfectly fitting and acceptable. Like maybe his voice was just a bit stressed back in the DotT days).