Check for Bluetooth timeout setting on stock Android 13
CalyxOS 4.3.0 (based on Android 13) has a "Bluetooth timeout" setting that automatically turns off Bluetooth if no devices are connected for a configurable amount of time (the timeout can also be disabled). This setting could prevent Briar from connecting to contacts via Bluetooth if the timeout period elapsed with no contact connections.
We should check whether this setting exists upstream (stock Android 13) and whether a timeout is enabled by default.