Directanywhere,
The stuffup with the offending washers was that they were COUNTERSUNK washers installed UPSIDE DOWN. This then creates stress raisers under the HIGH TENSILE boltheads,which eventually leads to cracks and ultimately,bolt FAILURE.
Pretty sure you or the pax don't want to see a 5 plus ton engine bouncing down the runway just on rotate or even worse departing the aircraft from 35000ft.
McHale.