xdcam-user.com think it may be detail correction (alisterchapman: Too much detail correction perhaps?) https://www.xdcam-user.com/2013/12/a-tale-of-two-cameras-the-pmw-300-and-pxw-z100-reviewed/
Hope it can be fixed in future firmware upgrade.
Yesterday I was working with Magic Bullet Look on a Z100 recording. I applied a custom curve and after that tried an Auto Shoulder. Highlights started to blink heavily from time to time. I removed Auto Shoulder and things go back to normal (very small blinking in very high contrast scenes).
I find a very representative scene with a fence against a white sky. Fence pieces become thin-thick-thin-thick from frame to frame if the camera is moving small steps (played frame by frame in Sony Vegas Pro).