There's often a uncertainty principle in songs as they are sung - there's a range of mini-variations within a particular variant; and likely enough a range of variants in addition.

I think expecting that a song can be fixed like a fly in amber is unrealistic. If it could be done it'd mean the song was probably dead. That doesn't mean that all the variations and the variants are equally good, or that there is anything wrong about someone who loves a song, and especially the person who wrote it, in the case of a recent song, trying to defend it against the kind of changes that weaken or distort it.