I'd like to report another bit of success. I brought over into RB that song that kept resetting the melody to Choir Aahs. Good ol' RB stripped out all that nonsense from the melody's info panel. So I saved the *.mgu file in RB and brought it back into BiaB and I was able to successfully configure the song's melody to my liking.

One peculiar thing I'm noticing about these songs that were straightened out by RB is RB strips out the last two or three measures from the melody. Not a big deal. I just copy and paste from an earlier part of the song. The song being an AABA format, this is easy to do.

So I have a game plan now. Whenever I run across a misbehaving song file, I'll just bring it into RB and that should straighten it out. Three for three so far.