how can I fix chubb lock?

When door is closed the chubb lock is not clicking into the slot so the door clicks shut. On the side where the handle is the square part of the lock keeps moving around and is not flushed to the door anymore. I have tried tightening screws but it still moves around. It looks as if it will fall off if handled too roughly and does not align to the door thereby causing it not to click when shut. Do I need to take whole lock off door by taking screws out to have a look inside lock to see if anything has come away.