Appears to be addressed in a 9.7 beta release:
BETA:
- Player: ensure correct external subtitle track is selected.
Unknown when 9.7 will go from beta to public release.
You can sideload a beta build if desired. Note that sideloaded apps do not update via the Google app store. You will need to delete & re-install the Google app store version to start receiving updates.
You can also join the beta program if desired.
