The problem usually comes down to one simple fact. Most hoselock connectors are made for one particular hose (ID and OD of hose important, hose that they usually sell as well) Even then it's likely that they drip as hose lock style connectors are just not great. The bright orange ones with black hose are actually pretty decent, as I've got two of them on a water meter right before the pre-filters, doesn't leak. Even at my parents place where they have much higher pressure it still doesn't leak. But they do leak if any different hose then the black rubbery hose is used. Ionics use them on their systems as well. The new metal hoseloc connectors are pretty good too, as apparently they have been designed to cope with different types of hoses. I've used them on a hot system hose reel before and the hose didn't come off nor did they leak. Due to their design they don't work on a van port though.
Another factor is that you need to change the O rings if they wear, as the system is new that's likely not the problem. O rings on male connectors (both sides). On water stop connectors there is usually also a small o ring on the back of the connector, which actually shuts the water off. All of these need to be renewed periodically, even if they visually look fine.