Faulty multipoint lock?

My Front UPVC door handle / lock is faulty. it is a 1 hook 3 deadlock and a latch multipoint fitted originally by anglian.

When i try to open the door the handle goes down but feels "spongy" and doesnt actually open the latch. To open the door i must first lift the handle to activate the multipoints then pull handle down and it opens perfect?

Can anyone advise what the problem may be and how i go about repairing this or would i need a full new multipoint system.

If it is a full new system i cant see on the bar any manufacturer so can i just measure and compare like for like.

Thanks