You probably never really did define a camera, you merely adjusted one of the 3 custom perspective views. Otherwise check the settings in the viewer and explicitly define your camera and also assign the "Always use this view for Previews" option to verify.
I in fact did create a custom camera. I named it "shotCam".
I just ticked the "Always preview this view" toggle, and the render still uses the native camera.
That confuded me is that it all works just fine in my "comp_05" comp, but when I select that comp in the project tab, press command-D to duplicate, and then render the new comp (comp_06), it forgets the custom camera.
Could you post a screenshot of your Timeline panel and Composition panel so that we can see how things are set up? I think that that might help with troubleshooting.
In that screenshot, the text is too tiny for me to make anything out.
I can tell that you're previewing in the Composition panel with your shotCam. But is that camera layer the active camera in the composition?
In case you're not clear on what the active camera is, here's an excerpt from After Effects Help:
"You can choose to view a composition through the active camera or through a named custom camera. The active camera is the topmost camera in the Timeline panel at the current time for which the Video switch is selected. The active camera view is the point of view used for creating final output and nesting compositions."