Contrary to popular belief, plants grown from feminized seeds are not truly female plants. Feminized and female are not one in the same...by the technical horticultural definition. So any time you run feminized seeds you may see unstable traits, or end up with a hermi. Some I of that depends on which technique they used to achieve feminized seeds. All involve unnatural stress and rely on a modern agricultural technique pioneered in the 70’s. It’s simply not something one may find in nature.
If you want a reliably female plant then you need to grow and select one from regular seeds. Learning through experiences like this is part of the game. Good luck