Dave, as I read your post, I think you might be on to something.

I think that the combination of "copy from....to....." and then "undo" might be confusing BIAB somehow.

When I think back of songs I've arranged, the simple ones where I enter melody notes, then lyrics without using "undo", those seemed to come out fine.

But when I recently put together the song "Dream On", I had 1 chorus and 93 bars. I was building it maybe 8 bars at a time using "copy from.... to....", then I would sometimes change my mind and use "undo" because I copied it to the wrong bar and start over again. Maybe it's those situations that causes the problem with the lyrics.