If Yandex.Browser cannot be launched due to an error in your profile, it will be launched in recovery mode with a new profile. In this case, you will see this message:
To restore data from your old profile:
After that, all your data will be transferred to your new profile from Yandex server.
If you failed to transfer data from your old profile to the new one, report the issue to Tech Support using the Feedback form.
For more information about syncing, see the section Browser syncing.