Door Lock problems...

[Orange '71 GMC]

Before I get finished with my power door locks/keyless entry, I need to address a small problem I have been having as of late with the driver side lock.

The problem is, sometimes it will lock fine, with the key or by pushing the knob. Sometimes, it will stick, and will not push down at all, nor can you lock it with the key. The way I have been getting around it is, after trying to lock it with the key, and not having any sucess, open the door back up, and work the inside handle a few times, and then, try again.
What I mean by sticking is, it just won't push now, like there is something blocking it from going down.

It almost seems like there is just something that needs adjusting in there. Can anyone tell me what I might can do, and how best to do it?

Thanks In Advance!
DLB