Sounds like a fault with the Passenger Door Module (PDM) located in the front passenger door it also controls the rear door. It could be a simple broken wire between the front passenger door and the A pillar.

My understanding from Haynes, and other data is that Fusion system is identical to the 02-08 Fiesta arrangement.

The GEM, behind the dash above the pedals, controls the individual door lock motors for both lock and unlock.  Drivers door has it's own "unlock" control, but the other three doors are fed from a soldered joint.  All "lock" signals are common to all four doors via another soldered joint.

I think I would start by checking the connector in the "A" post, passenger side, making sure connections are clean and connector done up fully.  this might find a fault for the front door.  There is also a connector to the rear door in the "B" post which might warrant a look.

I am also assuming that you do not have any "Door Open" indications.

If the doors always unlock, but do not lock, using the remote, then the motors clearly work, at least in one direction.  There is a micro switch in the motor circuit, which controls direction, and perhaps one contact (the lock) is high resistance in both these doors.  If this is the case, then repair is expensive as everything is in one module.......  The door open micro switch is not very reliable, so if the motor control switch is similar, then longevity may also be cut short.

What you could try is exercising the motor micro switches without any voltage/current across them. Disconnect the battery, and then lock and unlock the relevant doors using the release handle on the doors.  If the microswitches are the fault, then cleaning the contacts in this way might restore the correct function.

However if the fault is in the soldered joint from where the lock signal gets from the GEM to the door lock assembly, then good luck in finding it !