I have been modifying EGLL with afcad2 and recently changed the approach lights to CALVERT2

In flight when viewed from a distance they can been seen, but when i line up for landing all i see is the list part just before the threshhold. Is this some kind of scenery conflidt?
I thoguht it might be something to do with the airport boundary but i don't know how to change that (if indeed that is the problem) Any sugeestions greatly appreciated.
Vololiberista