KOHLER-still leaks

[Grazzy]

i have a K-3385 Rochelle that was leaking slightly, so i replaced the float ball and cleaned the brass housing. with the water cut off, the level dropped about a half inch over night. what can i do other than replace the ball again to stop this miniscule leak? a photo is in the link below.

https://terrylove.com/forums/showthread.php?t=895