What's the easiest way to cover up a seam in background paper behind video footage in Final Cut Pro? I have about 10 minutes of footage which includes what is supposed to be a 100% white background (no gradients).

The person who shot the footage apparently used 2 overlapping sheets of white background paper.

This left a horizontal line across the background.

It's really faint, but still noticeable.

Is there a relatively easy way to get rid of this without having to deal with it on a frame by frame basis?

(Note: to make matters worse, sometimes — though rarely — the line is directly behind the subject — a product being unboxed)
For the parts you have nothing in the way I would duplicate the clip above, them mask out a part without the seam and move this over the seam. 
When the product come over the seam I don’t see another solution then to track the mask frame by frame.