I'm on my second light engine, what is it that

If you have a blue glow,then that could be the color wheel has been chipped or shattered and blue is the only section remaining,not likely but very possible. If the color wheel by itself is not available for order as an OEM replacement part,then that may be why you were charged for a whole light engine.

it comes from a warped blue lcd filter that is in the optics for the light engine
they have developed upgrades for the air flow
most of these sets when taken apart are full of lint dust and the back louvers have not been attended to
id guess every week or two take your vacum and go over these to keep as much collected as possible
but it appears the lcd plates warp from heat build up
have changed a great deal of them