It turns out we had a file permissions issue due to the random users on OpenShift.
We corrected the following line to allow NGINX to read the configuration file and the problem was resolved:
# this chmod line is required on atomic but not on CDK - researching why (moriarty)
RUN chmod -R 777 /var/log/nginx /var/cache/nginx/ \
&& chmod -R 777 /var/run \
&& chmod -R 777 /etc/nginx/*