How do I calculate current x-axis rotation of a configurable joint and set it as target position?

I am using configurable joint (conjo) to rotate a Rigidbody object, by setting conjo's drive mode to 'velocity.'

When I stop the rotating conjo object, by setting the target velocity to 0, the conjo is powerless, that is, other object, forces and gravity can still rotate it. I don't want this.

One strategy is to switch from 'velocity' drive mode to 'position' drive mode when stopping. This can be done by reading the last rotation along x and use that value as target position in conjo. The question is, how to I calculate the current x rotation of the conjo and apply it as its target position?

I tried the following:

 if(stop) {
         myConjo.targetRotation = Quaternion.Euler(this.transform.localRotation.eulerAngles.x, 0, 0);
     }

However that little snippet does not work as I expected. Upon stopping the rotating object, the target rotation seem to go to another rotation that is different from this.transform.localRotation.eulerAngles.x.