Count Chockula in the mountinaproject.com forums writes: "This #0 rarely gets placed and has never been hung on or taken a single fall, but one of the cam stops has completely sheared off the lobe." The post is old (May 2011) but interesting. Metolious replaced the cam and have apparently made changes to the design since then.
In an apparently separate incident, another forum user Alan Ream shows a photo of his Master Cam, which also has broken cam stops. He shows it side by side with the newer design of stops - which appear to be slightly larger and no longer adjacent to grooves in the camming surface. Users speculated that the proximity of the stops to the grooves could have contributed to the failures.
Image from Alan Ream on mountainproject.com forums