It very well could be strain related. I am growing clones of a querkle seed that was from a selfed querkle clone from a seed that was from a selfed querkle clone. Basically sometimes the lower, inner buds get seeds, and those are guaranteed females. HOWEVER, they are also slightly unstable and fairly easy to go hermie. If I get them, I usually have a big run of hermies at week 4 or 5 of flower, (a few dozen throughout the 4 plants in flower). I pull them off. I have noticed that even the ones that are ripe don't have much pollen in them. They don't always hermie, but it doesn't take a disaster level stress to trigger it. I have had plants FULL of hermies that didn't have a seed in it, as well as plants with few to no male flowers, and dozens of seeds. Any hermies popping in the last 2 weeks or so usually wont cause mature seeds. If your flower area is staggered, then the hermies late in flower can pollinate the younger plants in the area. I used to have this problem, so I reverted to One grow, one cab. This should stop the production of mature seeds. While stress does cause hermies, people forget that growing sensimilla plants is stressful to begin with. Biological clock ticking, still not pregnant. Who needs a man, I can do this myself lol. Plant equivalent of artificial insemination!!