Not sure if you found a solution or not, but I will leave for others…
When you set your PYTHONWARNINGS variable in your compose file, remove the " character. Removing mine also removed the double quotation in the environment variables.
Thanks. I thought I tried that but still had the issue. I gave up and just put my Unifi behind my nginx reverse proxy. The OCD in me twitches at that, but, I have learned to live with it. 