Automatic sleep tracking stops before I wake up

On weekends, when I don’t have an alarm, the sleep tracking stops hours before I wake up. Today, for example, I wake up around 13:30, but the sleep tracking had already stopped at 9:15. Why is this, and how could I fix this?
All awake detection methods are enabled except for sound. I’d like to keep the sleep tracking automatic too, because I would never remember to start it manually.

Hello @grotesqueer, I would need to see a menu > report a bug, but either this is automatic sleep tracking which may end sleep tracking in the momrning of after expected sleep time and significant activity is measured… or this is non-standard app killing done by OEMs explained here