Remove front glass to clean dark smudges in corners

Sorry the cover glass and the LCD are a fused unit. You can’t separate them.

As to the smudges, it’s not dust! You have LCD persistence (burn-in) this is when a part of the screen has a static image which causes the liquid crystals to become stuck in the wrong state.

Sorry Dave this is a red herring! Hagens Berman are Class Action lawsuit ambulance chasers!

The seal between the cover glass and the LCD is complete! There is no means for dust to enter. I've got two systems both of which has this exact problem. I had a static photo as my background over the years it became burnt in. I've reduced the effect but its still present.