A few years ago I was lucky enough to buy a NIB 850AV monitor from a parts dealer on eBay. The video and sound from this monitor are both truly spectacular with one little issue: there is a dark/discolored spot at the bottom-right of the screen.

Degaussing using the built-in setting doesn't help of course. What can I do about this? Could there be a speaker shielding issue with one of the built in speakers that is causing this?

Thanks