Please note, that is the Sebenza 21. NOT THE 25.
I found similar.
Well....
Lets get to the point:
The ceramic ball lockup is supposed to look late, but in in reality is not.
"Those who have followed the nearly 25 years that the Sebenza has been around know we continually make small improvements, alterations, advances to our knives. None of these changes are made to follow a trend, to keep up with the Jones or to tick off our customers. They are done to improve performance, safety or production. That we make a change to the Umnumzaan should not come as a surprise.
The disc has been added to the Umnumzaan to prevent the reduction of tension on the lock. Because the shape of the Umnumzaan handle is a little different than that of the Sebenza, it takes a different technique to open and close. We have found some customers are not willing to learn the difference or perhaps they don’t recognize the difference but, whatever the reason, they think it is necessary to modify the lock tension, thinking the knife will open more easily. This simply makes the knife unsafe. We have had several Umnumzaans returned to us because of lock issues – almost always the customer denies having modified the lock. We can see what has been done, and are put between a rock and a hard place as we don’t want to call out the customer for not telling the truth. The disc is a solution to prevent potentially unsafe modifications.
Please note this disc is not a lock stabilizer as it has been called in some posts. It is simply in place to prevent the lock bar from being pushed out to reduce tension. Our locks are fitted properly to very close tolerances and do not need to be stabilized. And to save further speculation, the disc is press fit into the handle. It is made of 303 stainless steel, and is sandblasted along with the rest of the handle. Because it is not titanium, the sandblasted finish looks different.
Will it change further? Quite possibly. What might these changes be? No idea at this time.
It will be a while before you see Umnumzaans other than the Wilson Startac with this disc. This has to do with our on-hand inventory of machined handles.
We are not planning to add the lock override protection disc to the Sebenza. We do not have the issue of lock modification by customers to the same degree as we do with the Umnumzaan.
Before the question is asked here is a quick reminder of the difference in how to open an Umnumzaan and a Sebenza.
Umnumzaan: slide your thumb straight forward, parallel with the handle, pushing the lug with the top center of your thumb.
Sebenza: push the lug out sideways in a sweeping motion with the side of your thumb.
Since there has been renewed discussion about Idaho Made in this thread, you might find it interesting to note that since March this year, the value of our back orders has almost quadrupled. This would indicate there are not too many concerns about the Idaho Made marking.
We appreciate your loyalty and enthusiastic conversation. We know we can't please all of the people all of the time!
Anne"
http://www.bladeforums.com/forums/s...y-Umnumzaan!-Lock-Bar-Question?highlight=lock
further searches:
http://www.bladeforums.com/forums/showthread.php/701337-Umnumzaan-quot-lock-up-question
http://www.bladeforums.com/forums/s...tion-for-those-who-carry-and-use-an-umnumzaan
And then the cherry on the cake from the thread: Some Words from Chris
http://www.bladeforums.com/forums/showthread.php/730951-Some-words-from-Chris......
"The lock should engage at between 50% and 75% of travel. With the Umnumzaan, because the interface between the blade and the lock bar is a ceramic ball, it is the ball that must be at 50 – 75%. This will give the visual that the lock bar is further over than with a Sebenza."
I have yet to hear of a single lock with the ceramic ball interface that gives any problems. Since the release of the Umnumzaan, despite people complaints of it being "late" no one has had one wear out, disengage or develop any "sticky" lock.
There has been only reports of people overextending the lock resulting in problems and from there the CR over extension tab/disc or whatever was applied.
So, in short. Dont mess with what works and use it.
send it in, but by that time you'll be using a Sebenza 65 
Mine def feels like it's the most solid folding knife I own by the way!!
