So, it sounds like the factory threads in the frame stripped out. How does that make the bumper broken? The threads in the frame aren't that strong, that's why a lot of people just drill through and put longer bolts in with nuts on the end. Maybe it's time you do that?
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ChuckH
"Every morning when I wake up I know it's not going to get any better 'til I go back to sleep again!" Al Bundy