2002 Dodge Stratus door locks will unlock but not lock

All of my power door locks on my Dodge Stratus will unlock when I use the master lock switch OR when I use the fob.

However, none of the locks will lock when I use the master lock switch or the fob. When I try to lock, they move a little and make a sound like they are trying to lock. But they do not lock. On some rare occasions they will lock, but not 90% of the time so I lock them by hand.

Any ideas what is causing this for all locks?