When a container is updated, unraid first pull the new image, then stops the old container, deletes it and create a new container. If there is an error creating the container, the container is deleted from the list as it have not been created. This is how unraid works, so nothing we can do anything about.
You have to find out why the container can't be created again. Force update it and you will se the error. We can't help when you don't post logs or error messages.