Do not put WD40 in the lock, as it is not a lubricant - its a penetrant.
yes there is a common fault with these i guess you tried it with bonnet up but lock shut as if bonnet was closed???..it could be either barrel try wd40 into the barrel.it could be the link bar or lock itself hope this is some light on subject
WD40's lubrication properties are very short-lived. When that wears off in just a few hours, the WD40 will be sat in the lock, collecting all the dust dirt and filth that goes anywhere near it. The upshot is that your problem will soon return and be 10x worse than before.
To lubricate a lock i'd recommend a light oil or heat resistant PTFE lubricant.