Just to note: I didn't change pixy behavior in any way for Tits mod, but I do notice that game tends to bug out in some moments when there's instabilities in framerate. Generally speaking, I believe there's some chance of random bugs which might happen. Pixies tends to break first. Amilia's slave-monster market breaks sometimes too. And if you play CB all essences in all your slaves can suddenly be set to random values, which is rare random bug, but incredibly annoying.
Complex Breeding does change a way pixy work - they can be summoned via potion early in the game (before Flora appears), Slaves with Witch and Wizard professions can summon them at the start of the night. I don't think it's the cause of pixie's behavior, but it just might be... *shrug*
As for other non-recommended mods, I'd suggest to also not to use HealthPixyPlus (it can accidentally kill slaves which rest in monster cage) and OvumRejuvenation (it can break CB's womb enlarge mechanic).