<< "This seems to be the case - of the files Jonel posted that I checked, the ones that didn't work were all misaligned or free tempo. This is fine if you're simply playing the MIDI, but when importing it into BB or any DAW you need to manually align things." >>

Same here.
Another possible solution is to create a tempo map using the ACW. BIAB has a feature on the Master Track in the Mixer to create a mix and open it on the Audio Channel.

Opening the ACW then has the audio wave file automatically loaded and ready to create the tempo. Normally, the chords have also been analyzed, the key set, the Style muted etc. The midi file opens imported onto the Melodist Channel. I use the normal open command (F3) for this.

The Audio File can be muted or erased once the tempo map has been created.

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BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.