When you try to move a layer with a transparent logo or text in GIMP, sometimes the background layer moves.
By default the Move Tool selects the layer of the dragged pixel regardless of which layer is selected. The tool only selects the correct layer if the pixel has at least 25% opacity. If the pixel’s opacity is less than that, it selects the layer under it, usually the background layer.
To force the Move Tool to move the selected layer, select Move the active layer in the tool options, or press Shift while dragging the layer.