I just had the same problem with my 2015 XF SC 3.0 SC. last week.

I would lock car as normal by pressing little rubber piece on outside door lever. Within a few seconds I would get two beeps. I would go back to car and see that 3 doors were locked and the drivers door was not. After opining driver's door my alarm would go off.

At first this was an intermittent problem but by last week it was doing this two beep thing each time I locked the car.

Last week I brought car to dealer and they found a defectiver driver's door lock motor. They had the parts in stock and replaced the defective door lock motor and since then the problem has been resolved. Everything was covered by the warranty and it took them about 2.5 hours to do the job. I understand that inner door panel as well as glass needed to be removed for this job. Everything was put back nicely and they did not even leave a grease spot anywhere. Have been using the car since last Thursday when the work was done and zero problems with beeps and locking or unlocking doors. This could be the cause of your problems since the symptoms you described are identical to what I was experiencing.

Good luck!

 

@nmyers718, I had to take it in to a dealer and fortunately, it was still under warranty (by a couple of months only!) So I have no idea what the cost would be, but feel pretty confident that it wasn't something I could've fixed myself. I tried all the things on here, and none worked. The said it was just an electrical "fault" and I haven't had any more issues.
Good luck.

 

A easy way to check if the hood or trunk sensor is to blame. Just remove the electrical plug to the sensor and jump across the two pins. Now you have eliminated the sensor completely.

See if your symptoms have changed.
.
.
.