Brute + salvation broken inside bunker

I went in a story Magwytch swamp bunker, small dungeon, in the 3rd room after rest it was a defend the extractor bullshit, I activated it, a brute came, and when I beat them down to phase 2, it started randomly running around and regenerating to 100% in 1 tick. I beat it down 2-3 times to about 25% where it started to run around like a headless chicken again and regenerating to 100% multiple times..

I was using my new dauntless axe with Salvation spell the first time, and the spell effect was appear to have bugged as well, I saw the spell effect multiple times, all around the arena, loing after the healing was gone, 10-15 times wherever I shot it, the effect was not disappearing (no healing in it though) I eventually had to give up since it was impossible to beat due to numerous bugs.