.

You increased the attack-frequency, which means the invulnerability overdamage can kick in

Same issue, in 1.9.0 it works fine.
Here's a video (look at the health):
https://user-images.githubusercontent.com/35194709/141801517-26ce5317-7a64-4404-85b1-da747d3e2c18.mp4
On the default config.