Authentication cached for nuget feed?

I did the following:

  1. Setup a nuget feed to TeamCity private feed using a user name and password
  2. Used it successfully
  3. Removed the username/password in an attempt to use integrated authentication (octopus services running as user account)
  4. Used the test tool and it worked for a while
  5. At some stage (maybe after reboot) , it stopped working with a time out
  6. Setting a username/password worked again

Also changing the server url takes a long time, the UI sits there for minutes.