Door locks on my 69 C10

[bvb69C10]

I'm trying to find out if my door locks are working correctly. The only way I can lock my doors from the outside of the truck is with the key. I can't push the knob down to the lock position and then shut the door without the knob popping back up and the doors remaining unlocked. This happens whether or not I depress the button on the door handle as well. Is that the way they are designed, to be locked by only using a key from the outside?