I got a similar error the other day when i made a light,
Entity 299, Brush 0, Entity leaked .
after checking and rechecking without finding any entity outside the enclosed map area(s) I finally did another meta compile, and when the error came up again and it highlighted the light ( again ) i just deleted it. made a new light and placed it into the same spot and re-compiled and the error was gone.
I think it was just a glitch. I was cloning my lights also, got a light entity to a certain hight and started to clone them to make more and move into a new spot.
you could try deleting the highlighted entity and make a new one and see what happens.