Re: final lock doesn't work
With my limited experience in Ki Aikido, try this nikkyo pin experiment: Get a good uke that will try hard to get out of the pin. Have him lie down on his/her stomach and place his/her right arm perpendicular to the his/her body. Kneel down so that your knees touches the arm as if you are performing the finish. Place your left "unbendable arm" above the elbow (do not apply force as this will give your uke something to fight with). With your right hand, apply the nikkyo finish by sending the ki from your ukes fingertips back toward his/her head imagining a huge arc. Lastly, relax when you do this. Then, ask your uke to try and get out of the pin.
Your left unbendable are will provide a ceiling or a stop that the uke can't go beyond. Your right hand will provide the excruciating pain (just be carefull not to injure the hand). When done right, this example pin worked all the time in my training.
If you try the experiment, please post the result.