Incorrect ENTRYPOINT/CMD
The documentation states:
The default user for the container is set to 1000.
The entrypoint for the container is /usr/bin/kube-apiserver.
The Dockerfile does not appear to contain an ENTRYPOINT statement. Instead it has:
USER 1001
CMD ["/bin/sh"]
The Dockerfile should end with
USER 1000
ENTRYPOINT ["/usr/local/bin/kube-apiserver"]