Photo is leaving a stain behind after moving specific lines

[Nicolas29315381i1e3]

I have been working in photo shop since 2015 and I have not experience this before and I do not even know what to call it in order to find a solution. 

I have isolated the lines of a black and white image, and I intend to move some lines upwards by themselves to allow the artist to redraw them. I have done this for 30 of their pieces at this point with no problems what so ever.  

This one piece however is different, When I went thorugh the normal process, I was left with a "stain" of where the lines were. I do not know how they go there, and I can leave multiple "stains" if I move the lines, 

I would like to resolve this issue, because while I likely could just open a new project and start from scratch - which I'm fine with - what if I encounter this again and making a new project doesn't work? 

So here I am, thank you for at least reading, please help. 

[Bojan Živković]

A quick and simple solution is to fill the background layer with a solid white color. Please try this and let me know if it resolves the issue.

[Nicolas29315381i1e3]

The only unfortuante thing is that it's not on the background layer, it's on the same layer as the lines. and if moved again, it over rides the original black lines on the same layer if there is any.

[D Fosse]

...and the only possible why I can think of, is that the drawing has been used in a selection/mask somewhere along the way. But you didn't see it until now, because, of course, it was hidden by the drawing itself. This can quickly happen if you don't keep your eyes on the ball at all times (and who does).

If this happened to me, I'd just automatically assume something like that, fill like Bojan says, then move on and forget it.

[Nicolas29315381i1e3]

Would an accidental selection mask also explain why it erases lines no the same layer? and why it doesn't go away when I try to fill the background white?