If you have a different casing of the release group name in your filepath, that takes precedent over the group name at the end of the file path. For example:
from guessit import guessit
guessit("/mnt/user/Hellboy.2019.1080p.DS4K.BluRay.x265.TrueHD.Atmos.7.1-NOXXUS.mkv")['release_group']
# returns "NOXXUS" as expected
guessit("/mnt/user/noxxus/Hellboy.2019.1080p.DS4K.BluRay.x265.TrueHD.Atmos.7.1-NOXXUS.mkv")['release_group']
# returns "noxxus"
guessit("/mnt/user/noXxus/Hellboy.2019.1080p.DS4K.BluRay.x265.TrueHD.Atmos.7.1-NOXXUS.mkv")['release_group']
# returns noXxus
If you have a different casing of the release group name in your filepath, that takes precedent over the group name at the end of the file path. For example: