Blue haze/blob near the center and lower right corner.

Sony WEGA 50'' DLP, not sure of year. Blue haze/blob appears on tv in the middle and bottom right corner. Shape is not the same everytime, and slowly changes and relocates around the middle of the screen. Replaced lens, no change. Depending on what show is playing it can and can't be seen. However, say if the screen is showing snow, you can clearly see the blue areas. Over faces also it is very evident.