Songs change in the singing - typically someone singing songs they made themelves will change them over the years, consciously or unconsciously. For example, words that look right on the page wille elide into words that sing better.

It's not uncommon for people who regard an early version (which has been recorded) as holy writ to complain that the person who wrote it in the first place is getting the words wrong. Or the tune.

What matters is whether any changes are for the better, whoever makes them. If they are for the better they will probably be the words and tune that stick, in the long run anyway.

I always find myself turning to Sydney Carter when this comes up. "You change a word, you bend a note; did it work or didn't it? What you put down, in the end is nothing but a variant...There is nothing final in the songs I write...I would like them to keep on growing, like a tree. They have a form, I hope; so does a tree. But it is not fixed and final."

That doesn't mean anything goes - but the reason for resisting changes should be because they damage the song, not because they aren't quite what the person who made the song first put down.