Null Object and shape layers inverted

This can happen when using a two-node camera if the camera is down at the X, Z plane instead of toward the X, Y plane. The camera flips orientation when it passes the center of the Point of Interest due to a problem called gimbal lock. 

You can check this by looking at multiple views in the Composition Panel. Four views, Active Camera, Top, Left, and Front work well. You can sometimes solve the problem by adding a 3D null, parenting the new 3D null to the null that is moving the camera, and rotating the new null -90º in X to reorient the motion path. You can then delete the temporary null.

Maybe this short tutorial I created years ago will help:

If you are experiencing a camera flip due to gimbal lock, you can also sometimes solve the problem by adding a Point of Interest 3D null to the scene and using a simple pickwhip expression to tie the POI to the Null will solve that problem.

Without seeing some screenshots of the comp and timeline with the properties revealed nobody can tell you much, but chances are you simply run into a gimbal lock situation and the whole thing just has flipped over due to combining some rotations in an non-ideal way, including possibly having messed up the camera itself. In such situations it is usually best to just start over - unparent, reset all transforms, delete all keyframes, re-create the hierarchy.

Mylenium