Modify existing custom scenery

Hi guys, i need an help on an existing project. Time ago i created a project editing an existing airport, the problem is that i have issues understanding the way the saving works (apparently). There is a tower i created, i want to move it in another position but when i select the object and translate it, an other one instantly appears in that position, when i save and put it in the community folder, the tower is still in the original position. What am i doing wrong ?