Are you actually using the standard power adapters? Or are you using different ones you have bought?

One thing that will always kill an in-line power receptacle is any sideways stress during insertion or removal. You should ALWAYS pull it out in a straight line, perpendicular to the case. If there has ever been more than the amount of effort you would use to remove a cigarette from a packet, then it is more likely to be the incorrent external diameter of plug. There are three types around this sixe, 2.75 mm, 3 mm and 3.5 mm. You would be best advised using the empeg supplied one.

The plastic of the power receptacle is a semi-flexible one which doesn't break easily. The problem is a tiny switch leaf inside the assembly, which can be either bent permanently over against the contact, or crushed against it if you use an oversize connector. Turn your empeg around and look into the power receptacle; at the bottom you should see a small, curved metal leaf. It should protrude about 1.5 mm into the socket hole. If not, then it has been crushed.

The only way to fix it is to desolder it from the motherboard and replace it; it really does mean a return. Too be honest though, for it to happen twice on a relatively reliable component does tend to imply you are either being too heavy-handed or you are using the wrong plug in the socket...