Quote:
When I play the MGU file in BAIB, then Use VST/DXi Synth must be unticked, otherwise there is no sound from the track.


That is a clue.
If you check the Use VSTi/DXi synth box, you should be able to hear all tracks .. and render it as such.
Do you have the other settings as in the below image?
Or did you miss the additional settings?

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BiaB_DefaultSynth.jpg (7.58 KB, 99 downloads)

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