In 3d View under Properties panel, the Background Images placement has some really weird UX / UI. In my opinion it's so bad it can be considered broken, because more often than not I see artists opt-out of this and instead just use a textured plane in the viewport.
Which is sad, because the Background Images has advantages.
So the weird UI part is that, you see an X and Y input (which in itself I have never seen in blender before, just X and Y horizontal as separate inputs. [Fig. A in attached images] And the horrible UX is, the input doesn't correspond precise enough, I mean you click-drag the values and the image goes everywhere on the screen.
In my opinion, the proper UX / UI solution for an 3d artist would be, you are able to select the Background Image in 3d viewport, and translate / rotate / scale it just as any other 3d object. So the User experience is not different from what it would be to handle a 3d plane.
But a copy-paste fix, could be to look at the properties panel in the Node Editor for Background, and how it's designed. Where X, Y input are structured coherent with the rest of the user interface. Stacked vertically and coupled with a move button, that button and it's functionality would improve the current state how you move Background Images in 3D View.
[Fig. B in attached images]
*UX = User Experience
*UI = User Interface.