Problem with billboard terrain detail texture

Hi!
I'm making foliage using detail texture on unity terrain system and I have a problem with billboard option.
Our game has tilted-topdown camera and it changes to topdown camera when we are close to buildings. When I have billboard checked, grass is dissapearing after few seconds when my camera is on "topdown" position. It going back when camera is back to tilted-topdown position.
Problem doesn't appear when billboard option is unchecked, but then grass looks weird cuz tilted-topdown and ocasionally topdown camera position.

Do you have any solution for this issue?



Edit
For other people who could have the same problem - setting camera from x rotation 90 to 89 is solving the problem. What a stupid issue and even more stupid solution..