Ford Focus Saloon 2001 2litre?

All the doors lock when selected to lock with the remote key then the doors immediately unlock themselves without any prompt from me.The same happens when the same key is used to lock the doors manually.

Yesterday it all worked properly and nothing has happened inbetween times that could have changed matters.All the doors including the boot appear to be clear of any obvious obstruction and I can find nothing in the manual to explain this. Can you please help?