Bounce in place - some bounces do not produce new tracks
I am attempting to bounce MIDI tracks to audio. The project has 13 MIDI tracks - the first 4 tracks bounced as expected (each time producing a new track XXXX_bip). Using the very same options on the bounce in place dialog (see example below), the remaining 9 tracks are stubbornly refusing the produce a new audio track. The BIP process seems to process the track (the play cursor moves from left to right at the same speed as it did the first 4 times when it successfully bounced the first tracks. But when it is finished traversing the track, a new audio track does not appear.
All the tracks use the same MIDI Instrument, audio effects and bus assignments. When I "play" the MIDI, each track is producing audible output - so it can't be that Logic is detecting "silence" from the track. I can't identify anything "different" about the tracks that work vs. those that don't.
I've repeatedly tried to bounce with no improvement. I've tried restarting Logic - no change.
What might cause this? What else can I try?
Logic Pro 10.8.1
Macos 13.6.4 (Ventura)
MacBook Pro 14″, macOS 13.6