Nearly all modern external doors have multi-point locks installed in them. Door locks are opened and locked many times in one day. Over years of use, the internal springs and gears wear and eventually fail. Mishandling and incorrect operation of the lock will speed up this wear. It will start to become difficult to lock the door, or maybe require extra force to lock the door. Eventually the lock will stop functioning; leaving you unable to lock the door, or unable to open it.
The Private Security Authority is a government body set up to regulate the many sections of the security industry including burglar alarm installation, cash in transit vehicles and locksmiths. From the 1st of February 2017, any person who in the course of a business, trade or profession provides locksmith services including installing, opening, maintaining, repairing, or servicing of door and window locks, must have a PSA locksmith licence.