My project has 2 flows and 2 full score layouts. layout 1 covers flow 1 and layout 2 covers flow 2. I have multiple tabs open: layout 1, layout 2 (page), layout 2 (galley). If either layout 2 tab is selected and I export audio for flow 1, the output is 10 seconds of silence (presumably the reverb tail setting). Audio export works fine after selecting the layout 1 tab.
Dorico Version 5.0.20.2042 on Windows 11 Pro (10.0.22621 Build 22621)