I’m starting to think the seed was subject to herm since I did find it in some bud.
More than likely man. Although the suggestions of light leak/stress/too much nitrogen could be the culprit.
I know how you feel, you want to know what happened so it doesn't happen again.
That's the risk of bag seed. More of a chance of herms compared to reputable breeders.... so if using bagseed the what went wrong becomes a lot harder to determine.
On the other hand, if you're growing a strain you've run before that doesn't herm with your growing style... you'll still see nanners in most cases if you push the plant long enough. Last ditch effort to reproduce.
As I understand it, and if I'm wrong somebody please chime in and correct me, pushing a plant so long that it kicks out nanners and gives you seed (puuuuuushing it even longer to get those to ripen), will give you female seeds that aren't prone to nannering. Nannering lol
In this case any seeds you make from this plant are more than likely going to give you the same result as here.
Yah might want to hack, or at least isolate that bad girl if you can't keep up to those evil little dicks.