Electric current leakage problem of Macbook Pro

I ordered a 13 inch macbook pro a couple of weeks ago. I didn't expect highly on my new macbook as I'm not a big fan of Apple. A week after placing the order, it finally got delivered to me. I teared the seal off, took the machine out, plugged it in and pressed the power bottom -- everything was awesome but hold on -- my left wrist was tingling all the time if I put it on the keyboard. I slipped my finger over the aluminium surface and the closer it is to the plug jack the stronger the tingling feel is. Then I realized it is, without a doubt, an electric current leakage. I searched on google and found quite a number of similar cases on macbook pro as its frame is made of aluminum. I didn't know whether it is a design flaw or a user error, since if I use the three-pin plug this problem would dismiss, until my roommate's mbp was found no such problem. I called the Apple service center and they offered me an exchange of my laptop right away. But it took them decades to do the return, shipment and delivery things again. Hopefully I got another brand new mbp a week later.

Unfortunately... the same problem still exists, and even more seriously. This time the whole laptop is fallen -- electric current leakage is everywhere on the surface. I'm nothing but disappointed. Don't wanna waste more time on dealing with it over and over again. I'll just use the three-pin extended plug although it is much chunkier and heavier than the original one.

Everything else on this mac is just good by far. Amazing overall design and battery life. But I'm still confused about whether the electric current leakage of metalwares is just unavoidable or it is indeed a design flaw of Apple?