Custom dockerized Analyzer Image not found

Work Environment^

Problem Description

We used the following description setting up cortex and the docker engine to dockerize analyzers: https://blog.thehive-project.org/2019/11/20/unleash-the-power-of-dockerized-analyzers-in-5-minutes/

The custom analyzers defined in https://dl.bintray.com/thehive-project/cortexneurons/analyzers.json work pretty well. But our custom analyzers cannot be started.
Therefore we entered the path to our local analyzers in the application.conf:
analyzer
urls = [
#"https://dl.bintray.com/thehive-project/cortexneurons/analyzers.json"
"/etc/cortex/analyzers.json", #default analyzers
"/opt/cortex/analyzers/Cortex-Analyzers/analyzers" #custom local analyzers
]

The Docker image is created:
REPOSITORY TAG IMAGE ID CREATED SIZE
local/url_trace 1 d415f6fa29c7 39 minutes ago 911MB

The analyzers meta data:
{
"name": "URL_Trace",
"version": "1",
"author": "asdf",
"license": "asdf",
"url": "https://github.com/asdf",
"description": "asdf.",
"dataTypeList": ["url"],
"command": "URL_Trace/url_trace_analyzer.py",
"baseConfig": "URL_Trace",
"dockerImage": "local/url_trace:1",
"config": {
"service": "search"
}
}

After enabling the analyzer and starting a job, we receive the following error (under job history):
Image not found: local/url_trace:1

Do you have any clue how to fix that?