In my case, the loose pin was stuck in the power adapter. As the power jack is instable due to it's small size and soldered very well onto the board (I did not make it to remove it from the board), I replaced it by a bigger one. Of couse, that did not fit into the case anymore. I attached two cables to the board, layed them outside the case and attached a new power jack. Add some hot glue and and superglue and it's a lot more stable then ever before.