Well - had to deal with these (2 of those effing Cobb hangers split), making it 3/4 in about 4 years.
The examination of the fracture surface shows striations/beach marks suggesting a fatigue failure from vibrations, with the crack originating right at the upper hole. @whoosh’s (not really) orange jelly beans went in.
A pro tip: use a dead blow hammer to, ahem, assist with the installation on the upper hook. Sometimes there’s no substitute for brute force. I didn’t have one handy, so used a 5 lb club. A dumbbell prolly would’ve worked as well.