Dirty Roses:
Summer of 69. Not an intentional structure change, it's just that despite us having done it for several years, the drummer still can't sort out a fill for the end of the middle 8. TBH, we really ought to drop it.
Tainted Love. Just an ending that works for us.
Twist and Shout/La Bamba. We just do it as a medley at the end of the night, it's generally fairly random where we switch from one to the other and where the lead breaks come.
Paranoid. No structure change, it's just that I think I only play about 90% of the notes because my fingers don't work fast enough. I'd love to drop it.
I think that's it.
Bonnevilles:
Born on the Bayou. Not sure if we've done a structure change or not, haven't listened to the original since we rehearsed it earlier and worked out what we would do.
Off the top of my head, that's it.
It's not just cover bands who change structures, if you have a listen to the original "Don't you forget about me" off Glittering Prize and compare it to the live version on Live in the City of Light, there's quite a major restructure. And then try and find a Youtube video where Simple Minds play it the same as they do on that live album, rather than yet another way.
And I really don't know why it happens. I know the guitarist in the Bonnevilles has commented on how I play Sweet Child O' Mine because I play it as per record with the correct hold of two bars on the A at the end of the Em C B A bit, as does everyone else I've played it with, but another band that he plays with does it some different length (stuff that, I'm playing it the right length!). So once a mistake has established itself, it's often difficult to extract it.