I run two foci, a 1.8 and a 170. Try disconnecting the battery for 20 mins and reconnecting. The locking mech on the focus suffers badly in the cold weather if it has not been checked regularly. A higher the mileage and age also lead to locking faults if they have never been looked at.I had a similar problem on the ST200, the cold weather knocked out the rear passenger door mechanism, worked fine when the weather warmed up.
It might not work but worth a try.