AWX web and task containers stop working after config - drops DNS after some time

OS: Centos 7.4 ( a guest on vmware )
Docker version 17.12.0-ce, build c97c6d6

After a successful install, I was able to connect to the web interface and do some basic configuration ( add user, password change, add organization).
After about 20 minutes, the web interface times out (shows an internal server error) and I can no longer log on.

Connectivity is restored after restarting the docker service ( all 4 awx containers - I am using an external DB ). However it disconnects again after
a short while.

Tail of Logs from the awx_web container:

File “/var/lib/awx/venv/awx/lib/python2.7/site-packages/django/db/backends/postgresql/base.py”, line 176, in get_new_connection
connection = Database.connect(**conn_params)
File “/var/lib/awx/venv/awx/lib/python2.7/site-packages/psycopg2/init.py”, line 130, in connect
conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
django.db.utils.OperationalError: could not translate host name “tower-db-001” to address: Name or service not known

unable to load app 0 (mountpoint=‘’) (callable not found or import error)
*** no app loaded. going in full dynamic mode ***

I can see the failed resolution of the database name but it connected fine to the database during installation and I was able to logon and make config changes post install.
Also, if I restart the docker service, I can connect again. What changes in DNS after time?

Thanks in advance.