Props causing a leak.

[gray flame]

make sure the world brushes seal the level and no brush is an entity touching the void

is the leak caused by an areaportal not done right

does a wall have a window in it or a transparent texture on it that faces the void

post your vmf

brush is bad here, it could when the map is being compile vertices are moving and that whats causing the leak increase grid size to 8 then remake the brushes, you might find another leak because of more bad brush work so you'll have to do the same

load the portal file and follow the line from outside

at the bottom of H++ is some info the id is the selected brush and the grid size would further to the right of that

[gray flame]

its not the entities or models causing the leak it bad brush work :/ but i feel your pain