91 Astro alternator bracket

Got a 91 Astro with 157,000 miles, original motor and trans. 8 months ago the bracket for the alternator snapped. I got my hands on a replacement from a salvage yard. It broke again and took out my alternator with it. It actually took a chunk out of the casing. Any ideas why this has happened? I can see it being a fluke and it happened once, but twice within 8 months! i took a few pics to get a better look and its pretty wild.

Got a 91 Astro with 157,000 miles, original motor and trans. 8 months ago the bracket for the alternator snapped. I got my hands on a replacement from a salvage yard. It broke again and took out my alternator with it. It actually took a chunk out of the casing. Any ideas why this has happened? I can see it being a fluke and it happened once, but twice within 8 months! i took a few pics to get a better look and its pretty wild.
try finding a gmc they have a better bracket setup.chevys 1 steel bracket starts to bend at the powerstearing pump and will crack there after time.gmc uses 2 al. brackets.1 for alt.1 for ac & ps.dont for get the belt tensoner and the belt is smaller for the gmc setup. good luck with it 83 g20 305 700r4 88 astro 4.3 700r4 90 g30 5.7 400 turbo