Power Locks Locking and Unlocking On Their Own

Yesterday while I tried to unlock the van using the remote control, the doors failed to unlock the first few times. Thinking back, the locks didn't seem to unlock properly a number of times prior to yesterday. Anyway, when we went out, things seemed fine, but we had trouble unlocking the doors to get out. Finally, on the trip home, the locks began clicking as if the doors were trying to lock and unlock on their own. When we got home, I tried to use the remote but the locks weren't responding properly ... locks weren't unlocking. At one point, I tried to use the lock control button on the driver's side door, and nothing happened. Finally, we did get the door unlocked so that we could get out.

Any idea what the cause could be? What the fix could be? Can the auto-lock function be disabled safely so that we can just go manual?