as long as you're not able to replicate the bug and it does not persist after sleeping, it is not that important
Viewing post in Femdom City M.A.N.T.I.S. [0.8.1] First Endings Edition comments
This glitch is indeed replicable. To replicate it you have to open the settings menu, then close it, then open the character's stat information and close that. After doing so you will have infinite energy, but your willpower will still run out eventually.
Thanks alot for all the work you've put into this game by the way! It's really good and exactly to my kinky tastes :) I can't wait to see where you take it with further development!