I created a sample project, minimally modifying the HelloCordova project with a Download file button.
The File Transfer plugin is trying to download a single file through https (from my public dropbox folder. Any other file will do, as long as it is behind https).
I added NSLog calls in the didReceiveResponse and in the willSendRequestForAuthenticationChallange callbacks.
If I cancel the download after the didReceiveResponse starts (but before it is finished), and then try to download again and again, at ~ the 10th attempt the download just never starts (I used fiddler, and at that stage no request is coming out).
When I tried it in a different host, it was consistently after the 6th download attempt/cancel.
My sample project is located at https://github.com/ATGardner/cordova-FileTransfer-test
just run "cordova prepare" (and maybe add the NSLog calls in the CDVFileTransfer.m file)