These little generic version 1st stage regulator low-pressure over pressure relief valves (OPV) just do not live up to expectations. They are more of a "consumable" than a permanent device, in that they wear out. After a while they start to leak, a tiny dribble but they will leak eventually... and the deeper you go the more likely they will leak because their depth compensation is weak. When they start dribbling, just replace them because they can't be repaired. Best practice would be periodic replacement when you service the regulator. Seriously, they are c**p and instead we suggest you consider the branded Highland Rebuildable OPV.
So why DO we sell the generic version? Because they are widely used in the dive industry, plus we can't find a better quality value priced alternative. We sell them at what they are worth, which is not much, so at least we are not ripping you off and you can afford to buy several for replacement as required.