Link object data moves all the planks to the first plank position

Hello and thank you for this great tutorial. Most of my questions so far have been answered in previous discussions but now I feel a little stuck although I have found a temporary solution. After detailing the first wood plank while trying to link it to the other planks, with CTRL - L -> object data, all the planks dissappear. What happens actually is that they all change position and rotation according to the first plank. If I move them with snap, individually, eventually I obtain the result. But I wish to know where did I go wrong. Inspecting each plank, it seems they all have the same values for positions.