Without exception, they were broken internally, ie just when you thought the lead in your pencil was kosher, a little bit dropped out.
Off track, but if you want a wheeze with a colleagues lunch, take his Banana if he has one, insert a pin or needle down the black area of the skin and move it from side to side, either do once or repeat up its length. The result is when he peels it, the said banana falls out of the skin in either one bit or nice cleanly cut multiple slices, with no evidence to show as the skin tends to split down the black bit as peeled.