Two thin bright horizontal line through all screen

Hi guys 

Having issue with my Dell XPS 9530  15 inch

two thin horizontal lines appear through all dispay. they exactly divided display onto three equal parts.

those line visible only on dark solid color filling screen. External display is ok. Bios tests same result observable on dark , not visible on light. Looks like a problem with back lite. No falldowns, no drops labtop was moved only inside my apartment from one table to another,

Most inteesting it exactly same issue appearing second time. First 6-8 month after purchase. was replaced display under warranty. and now after -9 month after replacement EXACTLY same issue. 

Anybody have something similar? looks very possible engineering defect. And dell support offering me fix on my cost.

Thanks

Kostyantyn