Reboot Log produces two entries on os_mgmt and shell_os reset.

[mlaz]

Two reboot log entries (instead of one) are produced whenever the system is reset either from shell or from newtmgr (mcumgr).

[ccollins476ad]

The problem is that most apps call reboot_start() before configuration gets loaded from flash. Consequently, the log_reboot_written setting is always 0. This causes the firmware to write a new entry every time it boots up (even if it already wrote one when it shut down).