We have had no problems with these connectors (genuine German fittings not cheap Chinese copies) at all and have had no problems needing looking into.
The fact that you have had exactly the same problem with the replacements, makes me think that what might be leaking is where the hose joins on to the barb. Sometimes these can leak in such a way that it appears the leak is coming from the joint instead.
Have a really close look at exactly where the water is leaking out, I think that it is only leaking when connected which means that it probably is the connection between the pole hose and the male barb. If not done up exactly right the jubilee or O clip can allow a fine jet of water to squirt onto the joint.
If having examined this it really is the joint, then please send them back and we can check them out and arrange replacements.