While, I did find a ‘solution’ to this problem, though it might not be a great option for everyone. I ultimately downloaded a different PBR material that fitted my needs better anyway. This new material doesn’t seem to present any of the same issues, so based upon this and what I described in earlier posts, I think there was just something wrong with the normal map from the old material. Anyway, thanks to Sipci for doing their best to help, and hopefully someone will find this useful in the future.