Problem with Log4j in Docker image 'universalrobots/ursim_e-series'

When I run the simulator docker image (https://hub.docker.com/r/universalrobots/ursim_e-series) it reports missing Log4j files:

ERROR StatusLogger Log4j2 could not find a logging implementation. Please add log4j-core to the classpath. Using SimpleLogger to log to the console…

I can see there are multiple logging related files in the docker image, but apparently they are somehow not in the classpath:

/ursim/GUI/bundle/polyscope-java-logger-impl-1.2.88.jar
/ursim/GUI/bundle/polyscope-logging-impl-7.10.32.jar
/ursim/GUI/bundle/log4j-core-2.17.1.jar
/ursim/GUI/bundle/log4j-api-2.17.1.jar
/ursim/GUI/bundle/polyscope-logging-api-7.10.32.jar
/ursim/GUI/bundle/polyscope-java-logger-api-1.2.88.jar
/ursim/GUI/bundle/commons-logging-1.2.jar
/ursim/GUI/bundle/polyscope-logging-driver-7.10.32.jar

That is probably why my “LOGGER.warn” messages are not printed (whereas System.out.println is printed).

Please advice how I can enable Log4j?