Turbo 400 Case Connector Install

[CC Rider]

Is there a trick to installing these Turbo 400 case connectors? My original was replaced a month ago because it was severely leaking and loose. Bought another with an o-ring, dropped the pan, removed the old one which had a broken tab that I located, installed the new one and the pan, refilled the ATF, and all was good for about a month. The connector was tight, but now is somewhat loose and is leaking again.

Thinking about buying another connector and using a larger o-ring, or salvaging this one. Did I miss a step installing this one? BTW, the photo is upside down.

Thanks.