Black dots and stripes with cinecamera focus settings

I’m trying to get a shot with a cinecamera actor, but when I try to set the focus method to manual or tracking I am getting this black dots in the scene. The black dots and lines dissapears when I change the focus method of the camera to none, but I need the DOF in the take. Adjusting some values in the focus settings they get low, but still in the preview.

Working on an iMac 3,4 GHz Intel Core i7 - 16 GB 1333 MHz DDR3 - Graphics: AMD Radeon HD 6970M 2048 MB