curious issue with Sony HS10

Hi guys - had my HS10 now for 5000 (mostly happy) hours, regular filter changes etc. Replaced the blue "in" polarizer myself recently due to yellowing screen, perfecto! easy to do thanks to the help from this fine forum. Funnily enough though, now about three months on, another anomoly is raising it's head. The fringes of my screen (mainly bottom centre & bottom left) are becoming very blue. This alone is not catastrophic as its mainly in the excess light path that overflows around the picture of whatever I'm watching. However, the more I increse the brightness and a blue hue seems to dominate the top centre of my picture, not just the edges. It is not so strong when the picture is dominated by red/yellows; is slightly noticeable when greenish images are up, but is actually most noticeable in black scenes. I had a look at all the other in/out polarizers and none had any serious visible deterioration like on the one I replaced that was 1st in the light path. The blue "out" polarizer has some very slight deterioration but this does not match up with the zone on the screen. Also, just "to be sure", I rotated the blue OUT polarizer 180deg to see if the blueish patch shifted to the bottom and it didnt - all stayed exactly the same. hmmmmmmm... confused and wondering what the great ones from AVF can share with me?????
cheers
Julian