Your Icosphere also moves when you rotate the Empty about any of it’s axes other than it’s local Y (Key R YY, move mouse). It also moves when you move the Empty along any Global Axis, or it’s local Y axis (key G YY, etc.). This is all entirely predictable behaviour for a driver variable set to the variable object’s Local axes. To “cure” this behaviour, so it only moves when you move the empty along its local Y axis or Global Y axis, set the variable to Transform Space. To stop it moving when you move the empty along any other than the global Y axis, rotate the empty so its local axes align with the global axes. Otherwise if you move it along local X, this has a Y component if you have rotated the empty. Hope this is all clear!!!