Every time you try drag & drop a picture into the editor and save, when you open .osu file you will see that the background image has an offset of 1,1 (X,Y). By default this was always 0.
To replicate:
1) Open a map in editor that has no BG.
2) Drag & drop a picture (I used a 1366x768 pic) into the editor. You will be prompted if you want to use it as a background. Select yes.
3) Save.
4) Open .osu file and locate the line where your picture is added.
You will see something like this:
[Events]
//Background and Video events
0,0,<name of the pic>.jpg/png, 1,1
^ the above 1,1 should be 0,0 (or it shouldn't be there at all) or the picture will be moved by 1 pixel down and 1 to the right.
To replicate:
1) Open a map in editor that has no BG.
2) Drag & drop a picture (I used a 1366x768 pic) into the editor. You will be prompted if you want to use it as a background. Select yes.
3) Save.
4) Open .osu file and locate the line where your picture is added.
You will see something like this:
[Events]
//Background and Video events
0,0,<name of the pic>.jpg/png, 1,1
^ the above 1,1 should be 0,0 (or it shouldn't be there at all) or the picture will be moved by 1 pixel down and 1 to the right.