Tighten the bolt more.. I've had plenty through the years that seeped, never broken a banjo bolt.. The copper washer needs to conform top any irregularities in the surface it is sealing, they don't conform easily... If your worried about the bolt being over stressed replace the bolt after using it to force the washers to conform to the caliper & hose surface.. But before you do test to be sure the leak is gone.. That way when the new bolt leaks you'll feel OK about torquing the new bolt...