Smudges behind my screen Mits WD 65833 during black screens

Hello all. I have a WD-65833. Started noticing some smudging on the left third of the screen. I figured my kids must have put their grubby little hands on. I tried to clean it with the cloth I got from the TV. It became obvious to me that the smudging was not on the outside of the screen, but the inside.

It is not at all noticeable when the room is filled with plenty of ambient light, but during evening and night TV watching, there it is. Of course I made sure it was not a result of background lights (the pattern is exactly the same in this house as it was in my old house). In any event, the smudging is especially noticeable when the background is dark. So I figure it is either dust on the inside of the screen or on the lamp itself.

It just so happens that one of my HDMI inputs went bad on me. I had a tech from Best Buy's Geek Squad come out to diagnose the problem. He told me that he had to replace the circuit board. I also asked him about the smudging issue. He said he could not see it, then hooked the TV up to some equipment that ran through a series of black level tests and could not see it. I told him he would not be able to see it unless he were to come back when there was no ambient light. He basically blew me off.

I called Magnolia HiFi and explained the situation to them. They said they knew of the complaint and that it was common. They said the tech would have to take the screen off and clean the inside where the dust had accumulated. They also suggested that the tech knew what the issue was and was just acting ignorant. Well fast forward 6 weeks (the part finally came in) and the tech comes back out to my house (same tech). He starts to remove the back panel of the TV to replace the board. I tell him about my conversation with Magnolia and that they said he would need to take the screen off to clean the dust. The tech gets all pissy about it and says he is not going to do it. I said fine, I am just going to call his manager. The tech then decides not to replace the bad circuit board and says I will have to reschedule the appointment to have the lead tech come out. I said "you have got to be kidding me!" Then the tech says, you know what, I am just going to tell them to replace your TV.

I cannot believe they are going to replace my TV because the tech refuses to clean the screen. What a joke!