According to the Unofficial Elder Scrolls Pages, health should increase by 10% of Endurance, the base Endurance plus the bonus from the Lady birthsign. Upon leveling up, I only received health from my base Endurance.
My Endurance is 40 + 25 from the Lady birthsign. I should get 6.5 health per level up, but I only got 4.
UESP does not list the Lady birthsign adding to health as a bug, so I assume it was intended.
Incorrect health increase upon level up
Re: Incorrect health increase upon level up
This is a sideeffect of a different bug where birthsign stat abilities don't work the same way as vanilla.