I am using item 5, and got the same problem.The problem is at the interface of 2 and 5.
The pins on 2 are too short, or the small copper plates on 5 are too much "digged" in part 5.
I have tried to push up the copper plate, but dont find the solution to do it with a small screw driver. Is it possible to have a drawing that explain how these plates are mounted ?
As a temporary solution, I use some small aluminum plates to improve the contact.
I have the same problem with the connection of 6 + 5 + 2: I have to keep pressing 6+5+2 to give my DreamPlug any power.
For the moment I've disconnected part 2 and use an external 5V powersupply...
edit: I've just found out that my connection problem is with part 5:
one of the pins does not make a good connection with the metal strip (that should transfers the power to part 2).
It only works if I press that pin really hard...