I’ve stopped using ERA products. Their high-end nightlatch isn’t too bad, however. The version pictured does have one major design fault, though. (I’m talking here about the auto-deadlocking lock, top of the range but one; where there is a keyway in the inside handle and where there is an anti-slip trigger – the tiny little projection above the main latch bolt, but no kite mark. The very top of the range – the one with the kite mark – has four fixing screws (actually two machine screws and two wood screws) and doesn’t normally suffer from the problem.)
The bevel on the latchbolt is the wrong shape. Because it’s a latch, i.e. it locks as you pull the door to, one side of the latchbolt is sloped. Well on this latch it’s not sloped enough. Instead of being smoothly pushed in as the door is shut, the latchbolt resists being pushed in. The result is that gradually, the lock is hammered off the door.
This can be compounded if an inexperienced carpenter or locksmith has not secured the lock to the door with screws placed in the outermost fixing holes of the lock, but instead has used the innermost holes that ERA, also inexplicably, provide.
So if you recognize that you have this lock, once a month you should put a smear of heavy grease — car grease will do nicely — on the bevel of the lock’s bolt where it hits the keep’s strike. The lock will be on the door and the keep will be on the frame (unless your fitter was really incompetent). In the picture above, the bolt is at the left and the flat is facing us; the bevel is behind. The extra little dingus sticking out of the lock on the left is the anti-slip device that stops the commonest way of opening a latched front door without a key.