My understanding of what's happening with the HP is
- the first hit makes the HP of the enemy go up
- the second hit does damage as intended for the god mode
- this pattern repeats for every combo hit
I believe the crashes are related to this matter, and happens much more often when an enemy is left alive with "infinite HP". Although it does not happen every single time you don't kill an enemy.
Making sure to do "even number hits" to each enemy should prevent most if not all of the crashes.
This is what I understood from my tests, hope it helps.