On close examination, I found the metal stub for fixing the location of the leg when extended, was distorted. That metal stub was extrusion molded.
So, I ended up drilling a hole through the stub!
See another leg for comparison:
In order to serve the function of the stub, I placed a M2 screw through it, it's a bit long but it works.
It's not perfect but it works. I shall look for replacement when there's a discount. I could live with this one certainly.