16 energy would be consistent with having 2 animalistic tattoos. Probably v0.5.24b.
The animalistic tattoos haven't worked correctly until v0.5.24c. Before v0.5.23c there was no code to apply them to anyone, in v0.5.24a players also could use them. So for the previous 2 to 4 versions, those tattoos have been sabotaging people.
Viewing post in Energy bug - not replenishing
1) Open /files/scripts/effects.gd
2) Go to the bottom (not sure if my file has different line number)
3) Find the following:
func animalistic1(person):
person.energy = 8
func animalistic2(person):
person.energy = 16
func animalistic3(person):
person.energy = 25
4) Replace those lines with the following (Don't change formatting - just add the "+" in the right place):
func animalistic1(person): person.energy += 8
func animalistic2(person): person.energy += 16
func animalistic3(person): person.energy += 25
5) ...
6) Profit
5) Download my quick fix: https://itch.io/t/451573/cant-raise-the-children-of-slaves-after-they-give-birth...
The tattoo issue was fairly minor. Either use both fixes or just update to get the third fix(selling multiple slaves).