Alternator cover boxer 05

[chas]

Have just discovered my 2nd alternator cover as broken away from its 2 bolt on points , the metal shows all the signs of metal fatigued. The first one came off after the bolts sheared. I am at a loss to explain this as surely normal vibration from the engine should not cause this. The Boxer 2 litre TD as done 8000 miles and the shield was found lying on top of the alternator. Anyone else with the same engine experienced this sort of thing? Its still in its warranty period but off course I have the bugbear of going back and forth to get it fixed. I could understand if it was made from flimsy plastic, but the metal brackets are quite thick. chas