Yes they are supposed to work that way - a new behavior will take over from the current one. For your situation, just use a deactivated "dummy" layer, like a shape, as the framing source object - that way you can mover your layers, leave the dummy alone, and the camera will stay where it landed.
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Mark Spencer
Freelance Producer/Editor/Motion Graphics Artist
Apple-certified Master Trainer
Author, Motion 4 from Peachpit Press
http://www.applemotion.net