Compiling between 2.3.38 and 2.5.2, a portal surface I am using no longer seems to work - i did compile exact same map to check this. Any one able to confirm they also find this?
I do get a 24% reduction in light compile time though 
Also I find that where an ASE model has a face with verts all at the same height the clipping no longer works or becomes confused. This also seems to lead to strange lighting effects - it is almost as though the face is bing translated to slightly different co-ordinates and casting shadows there - except the face drawn in game is in the correct place.
Is this issue known?