Last year I hung all our butternuts with wire through the stems and had no problems with them dropping.
This year, a different story. Out of the whole crop (700+ lbs) 3 have fallen leaving their stems hanging above in the cellar rafters. The only difference between the two years that I can think of is I picked these a tad earlier in the Fall due to travel plans. You folks tend to have a shorter growing season and might have more of a problem. It is also possible that these have cross-bred with something else that isn't quite so stable :-\