So from what you writing i can guess that it's just appeared and before it was working fine?
You need some one with donor LCD it's hard to tell without any test, i would start with checking LCD connector and check how it will work with other LCD.
Even it's new i had refurb switches from Nintendo that assembled like garbage inside and i know 100% no one accept Nintendo where "inside".
Also never exclude factory defect's what's why we have warranties...