question about door locks on supercab f250
 

So i just bought a 09 f250 supercab and the locks on the front door locks dont want to push down and i cant seems to find the part for sale anywhere the part number should be 21813 and my second issue is with the driver side rear door i took it apart to try and see if one of the cables got snapped or came loose but they look fine i can see the top lock open but the bottom one wont budge even with the cable going to it moving it doesnt appear to be snapped anywhere but not sure how i can actually access it to look better without being able to open the door any advice is greatly appreciated

A lot of times this type problem is eliminated by spraying some penetrating oil into the door lock assy