panasonic projector weird problem ?

youtube video uploaded


panasonic projector pt st 10u 3lcd - weird problem - when turned on displays properly but after sometime all side boundaries becoming blackened slowly - projector working properly - not opened projector cabinet but checked exhaust fan working , 2 snail fans for air intake working - i dont know is there any 3 rd fan inside or not

---------what might be the issue - polarizer , lcd cleaning - or any fan inside not working (overheating issue) - anybody any guess ?

i disconnected the blue lcd ribbon cable then the picture has no problem but startup blue logo panasonic is only gone but video playing normal only in green and red colour - but my doubt is if blue colour lcd is gone wrong how then clear blue colour logo of panasonic is displayed when blue colour lcd is connected ?

so still a doubt is it blue lcd panel or polarizer of blue lcd panel ?