Using Synology-Docker to update your Synology Docker package is known to bring a few issues. They are listed below, including their workaround if available.

• Docker returns "failed to initialize logging driver" after updating - Synology implemented a custom logging driver called db, which is not supported by the Docker binaries installed by syno_docker_update.sh. The script updates the default logging driver to json-file to address this. However, containers that were started prior to the update might still refer to the now obsolete db driver. Removing and restarting the container(s) should fix the error.
• Containers cannot be reached in user-defined bridge mode (see Cannot reach containers attached to user-defined bridge network #35) - Setting up Docker on your Synology with the synology-docker script might result in difficulty connecting with containers in user-defined bridge mode. The default bridge network should work. Potential workarounds are to deploy your services in a Docker stack, to setup a macvlan network, or to use host networking.
• The update is incompatible with BTRFS volumes (see Updated binaries are incompatible with btrfs #22) - Launching containers could result in an error Failed to create btrfs snapshot: inappropriate ioctl for device on volumes formatted with BTRFS. @frobnicaty recommends to use Synology's BTRFS driver, which can be found in /usr/sbin/btrfs. Run which btrfs to test which driver you are currently using.
• Docker service can be prevented from shutting down properly (see Add timeout functionality #20) - The synoservicectl daemon (DSM 6) does not always terminate as expected, possibly due to a conflict with Docker's live restore functionality. Home Assistant is a known example to use live restore. Manually shutting down the container(s) will ensure Synology-Docker runs correctly.
• Containers cannot be launched via Docker UI (see Containers cannot be launched via Docker UI #21) - The Synology Docker package comes with a user interface (UI) to monitor and launch containers. Unfortunately, the launching of containers via the UI no longer works after having upgraded Docker with Synology-Docker. This could be caused by the specific Docker logging driver of Synology. Launching containers from the command line (via either Docker or Docker Compose) still works. Portainer could also be an alternative, but has not been tested by the author yet.
• Containers have lost their environment variables - As a potential side-effect, containers that exist before the update may lose their environment variables. It's highly recommended to define the containers in a Docker Compose file instead, so it's easier to recreate them on the fly.