Never mind ex Halton brats, this basic mechanic knows that the second thing to do after squarely drilling a hole is to de-bur. Not read the story but at what point has this fault been found, must be more to it surely.
I'm an ex rigger after I left I worked for a civvie company doing major upgrades on the Tucano at Scampton.
Never mind "de burred" holes, on these things we found holes 6 inches wide that had been chain drilled out but that was it all the drilled edges were left "Ragged", Glad I did not fly in them