The GetExactDeviceInfo error was discarded and every failure reported as
"DeviceInfo.xml is not persisted", so a malformed file or an I/O error was
diagnosed as a missing sync and the user was told to run Data Sync, which is
the wrong remedy for either.
Include the cause, as the neighbouring branches already do.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>