Why does Unity lock the transform of prefabs in my scene in playmode?

I made a script, that moves all Objects in the scene (exept for the character) move backwards (I created an empty parent object), to create the llusion, that the character is moving. But unfortuanetly it only moved objects, that were no prefabs, the prefabs were locked in the current transform. But in normal edit mode, I could move everything. How can I fix that? Please help!