!
I had some herm pollination in my last two grows(mostly ace strains) ,mostly from purple mexican(cannabiogen)and zamal hashplant(as I see in the offsprings).
I grew some of them this summer in a room with a glass roof(but with not good orientation)under natural lighting,something like a greenhouse in the shade.Not very good conditions,heat stress mostly and some light stress ,too.They performed very well for my standards and not a single nana I've seen.I was and still am too scared to try them indoors,but a friend(one of those who dare) grew some indoors and not a single nana again.Probably the herming was to my fault(a light leak,maybe ) .
Given that you grow flawlessly ,you 're possibly right that it's a genetic issue ,so very probably passed to the offspring.But ,yeah,I'd still grow them outdoors.Isn't also the glue a result of such a cross anyway?(and many more known cuts are said to be not just herm crosses but s1's) .
Anyways,thanks again for the great grow show you're offering us
Can´t be the genetics with so many diff strains hermin on me- My guess is a light leak, cause most of the plants are looking very healthy. As my tent gets older the Zippers and the seams are not what they used to be and to ease the watering schedule their daytime was from 2 pm to 2 am. Could be sun light penetrating thru the blinds during their night time. I plucked off every sack I could find and hope that the plants in the back not got hit by pollen. I also adjusted their daytime to the actual daytime to make sure it´s dark outside, when they are sleeping.
All the work and passion that went into this and now I have to smoke seeded bud for the next half a year...
The smoke is gonna be top notch anyway though (and that's what matters since it's for you) and I really believe it is a blessing in disguise,anything happens for a reason.At least keep some,you never know.Good luck man 
Ah,bummer...
