But once out of hundreds of queens is more of a fluke than a pattern.
In your neighborhood it was a fluke. In mine it was more. Out of thirty hives regressed to 5.1, then placed on 4.9, one queen absolutely would not lay in the 4.9 and, as I said before, several others were very sporadic in the 4.9.
Experience is a hard teacher because she gives the test first, the lesson afterwards