Bad Request (400)

Check DJANGO_ALLOWED_HOSTS environment variable. It must be either * to allow all hosts or be a comma separated list of hosts which can be used to access your installation (can be just one host)

Found another file with the destination path ...

When starting you see messages in log:

Found another file with the destination path 'admin/js/prepopulate.js'. It will be ignored since only the first encountered file is collected. If this is not what you want, make sure every static file has a unique path.
Found another file with the destination path 'admin/js/timeparse.js'. It will be ignored since only the first encountered file is collected. If this is not what you want, make sure every static file has a unique path.

This is normal, as grapelli django admin uses same static files names as django.contrib.admin (default django admin)

Name does not resolve

You cannot open a RDP/VNC/SSH connections and in logs you see message:

2019-10-28 09:13:19,494 ERROR Exception inside application: [Errno -2] Name does not resolve

File "/usr/local/lib/python3.7/socket.py", line 707, in create_connection
for res in getaddrinfo(host, port, 0, SOCK_STREAM):
File "/usr/local/lib/python3.7/socket.py", line 748, in getaddrinfo
for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
[Errno -2] Name does not resolve

This means that Guacozy cannot connect to guacd server.

When application starts a default Guacd Server is created with hostname=guacd and port=4822 .
This Guacd Server is set as a default in Application Settings

If you are not running docker-compose with "guacd" service you have to specify your own guacd server by creating a new Guacd Server object and setting it as default in Application Settings