Why do all pieces of a model suddenly turn during Animation? I have a 3D-model in the collada (.dae) format. Its a class hierarchy of pieces. All rotation modifiers and correct parenting have been applied to the model previous to starting animating. The model is in t-pose. If you want to take  a look at it - here it is:

https://github.com/PicassoCT/MOSAIC/blob/master/objects3d/asset.DAE

Once i start animating, everything seems to work as expected, i can set keys, make  a first cycle. Then, in Animation view of a general blenderscene, if i click on a seemingly random piece of the model and apply a rotation, the same rotation is applied to all pieces, and to all piece positions depending on there parent. 

The pieces look like a small planetary system, with the torso in the center.

Is this a bug, or do i use the rotation key system wrong? All rotations used are normal euler rotations. I will attach the blender files as another link:

Blender file with a rough walk cycle
Maybe deactivate the Proportional Editing option? Shortcut O to activate or deactivate.