Keyframing effects initial pose randomly

Hello, i’m going through a difficulty with my armatures.
I use makehuman’s vanilla armature.

I begin by keyframing the whole character in the first frame, then i jump to a further frame, rotate the bone (using G key) and keyframe it using rotate. Then i check my initial pose and it is OK.

But after doing the same for a few more bones, my initial pose gets affected from my changes in other frames (as if i rotated and keyframed them together.).
The file shows the step just after the mishap.

Attachments

rigmischief.blend (1.1 MB)

It may help you to remove the shape of the bone so you can see.
One bone move as it is keyed and it is influencing the other. the other is moving with influence from the parent bone then continues to move with its own keying after the parent bone stops rotation.
You can see in the dope sheet they are only moving as they are keyed. Check the arrow icon in the dope sheet to see only selected bones.

But how do my changes affect the first frame?