When your multimeter expose to moisture,sunlight or aged. The lcd display will degrade slowly and finally leave black spot(or big one) on lcd display. However you don't have to worry, you can repair it without paying any money.
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Step 1: Here Is the Video of How to Repair Lcd Display Problem of Mine.
All you need is screw driver and something from your trash can.
I hope you save your money with my method.