The templates are by default stored inside the docker container.
When you recreate the container, templates are lost.
You can mount your external directory to the container to let it persist templates there.
See the docker readme "Persist templates"
https://hub.docker.com/r/jsreport/jsreport/
In case you use azure web apps, you may want to use a database or azure blob storage for persisting.
https://jsreport.net/blog/render-reports-using-azure-app-service