Something weird with the rig and child of - constraint

So, I added some controllers to the SIM4studio rig.

But then I ran into a problem.

I add a constraint - child of

on the bone - b_L_Foot and the right side

Only the xyz rotation that's ticked.

This constraint works perfectly in the pose mode.

But not in the object mode, like the image above.

The foot bones stuck in place.

I tested with other bones, all behave the same. 

I tested using new files, added some simple bones myself and added the constraint. It didn't behave like the rig. I can move the bone with the constraint, in the pose and in the object mode.

So does anyone has a clue why the rig behaves like it does?

Update:
So I make a test.

Using the sims4studio rig file, I delete all the bones  and create two bones only. A and B.

To Bone B, I use the constraint - child of, with the same settings only xyz rotation.
Bone B parented to A using ctrl+P.

Then, I move bone A in pose and object mode. And it behaves the same like the above.

But if I create a new file and repeat everything, the bone B will move along with bone A in the pose mode and object mode.

What's going on here?

Is there some kind of  a global setting affecting this?