"Simon"
"Did you render a WAV file of your song and save it in the same directory with the same file name? If so, change the name of the WAV file to something else. BIAB automatically loads WAV files with the same name onto the Melody track, which turns it orange exactly how you're describing."

That's the strange thing, I never rendered anything.
I just chose the style, changed a few instruments and the drums, put in the chords, saved the song, closed BIAB.
Next morning I loaded up the song, and the melody name had changed and turned orange.

It hasn't happened since.
It was probably something I did, it was kind of late.
...
"Did you re-generate the song? Or were the drums frozen? Choosing a different Realdrum does not usually force regeneration."

Yes, I always regenerate.
Thanks for letting me know that the bug is with 'Multi Styles'

I won't use them anymore until we get a fix.👍

Band in a box 2024, Build 1114, Windows 10, 32 GB RAM, Intel Core i5-940F 2.9 GHz