Why is there some duplicated edges pattern repetitively?


#1

Why is there some duplicated edges pattern repetitively?
Why is there remained part when I removed? This remained part seems like a duplicate of the edge of FG, and it is along with the roto shape of the removed part. Why?
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Let me rephrase :), Sometimes we have FG covering the removed part, so we have to roto them and put them on the top layer. Everytime when I click remove, around the FG, there are some duplicated pattern of the edge of FG. Like the attached below, the edge of FG (red sofa) are duplicated many times.

What is the problem with my roto and how to avoid this problem?