Hi Charlie,
I think you and others may have hit upon my problem. Too many chords and such when I create an ending, I've tried simplifying what chords I'm putting in which bars in the tag and ending and that seems to have helped. I've also discovered (derrr) that hitting "generate and play" after a change funnily enough seems to reset the song with any changes I made. Yep, probably pretty obvious when you think about it I suppose.

Thanks again for everyone's assistance.

Andy