Are you sure that you're looking t the scene through the same camera? Is it possible that you switched camera? You could create a new camera in order to avoid using the  default one or the Perspective view, the latter not being a real camera, and once you have the scene framed right, select the camera in the scene pane so that it becomes the active object and then  you can press 'Shift-L" to lock it. This will prevent any parameter to be changed until you unlock the object.

Paolo

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