I haven't read the original study.
https://www.independent.co.uk/news/a-drop-in-temperature-can-change-the-sex-of-chickens-1238516.html
Speak to some of the chicken keepers were I live and you may get told that hens have the ability to determine the sexes of the chicks they hatch. I read a long time ago a study that suggested there may be some truth in this, but didn't understand how such a mechanism could work.
With the study mentioned above and now the research being undertaken by the egg and hatchery industry, plus the offshoot studies from this paper,
http://www.scielo.br/scielo.php?pid=S1516-635X2016000600001&script=sci_arttext
it seems possible that a hen could influence the sexes of the hatch given she can control the temperature.
Now all we need to know is if the hen can and does alter egg temperatures with intent.
If she can then you need to have a word with your hen or adjust your incubator temps accordingly.