The front passenger door doesn't always unlock when I use the key fob. The only way to remedy is to lock and unlock the car again, sometimes even that takes 2 or 3 attempts. The garage couldn't recreate the issue so weren't able to diagnose. Has anyone experienced this and managed to fix? Is it worth me going to an official Ford dealer? So far I have only been to an independent garage who claim to have all the Ford diagnostic kit.

Most likely the door latch mechanism getting worn.  Any garage should be able to swap it successfully.  Doesn't need to be programmed but it does need to be correct for the vehicle.  Front, back, left & right are all different.  Keyless entry uses a different latch again.

This is an example but may not be correct for your car.

FORD FOCUS MK3 2011-2018 PASSENGER SIDE FRONT DOOR LOCK LATCH BM5AA21813DB#54058 | eBay

Try fully lubricating it first, remove the door card and lubricate it inside

Thanks both, will take a look on the weekend. Will WD40 be ok?

3 hours ago, hiace_drifter said:

Thanks both, will take a look on the weekend. Will WD40 be ok?

Ideally, you should use 3 in 1 oil spray, you want to lubricate the mechanism. WD40 is primarily a water repellent, though it won't do any harm, you'd be better of using 'oil'...

On 3/14/2023 at 2:43 PM, DaveT70 said:

Try fully lubricating it first, remove the door card and lubricate it inside

I found this video on door card removal ... 

Will give it a go, looks doable.

Bizarrely, I had to replace the door mirror on the same door, and that has solved the locking issue! I imagine the door lock/unlock command checks the mirror position, and was getting confused by the faulty mirror.