https://www.youtube.com/watch?v=E9uskQY37JM

Took several hits to show that I'm not regaining health. You can see that even as the orange bar is decreasing I continue to attack and nothing is gained. It would suck if I need to recreate the dungeon again to stop the glitch.

Is this a known thing? Has anyone else run into this?

Definitely a bug, I ran into the same thing myself. At the time I just chalked it up to another layer of bullshit to the fight.

It seems unrelated to memory leak because I've seen videos of him locked into only using swipe attacks and the player was still able to rally. No idea on a fix, but it's the only place in the game where I had this problem. I don't think it's worth remaking though, you wanna try to stay topped off against this guy anyway.

Only way I found to take on that boss was really learning his attack patterns and only attacking when I, for sure, wouldn't get hit. And you can only really get in one attack at a time, so might as well be a jumping attack. Takes awhile to chip at his health, but its the only way I could figure out how to beat him. And I didn't even notice that glitch because I could never land more than 2 hits on him anyway.

Glitched.

However, you can finish this boss without the regain mechanic, since he doesn't let you fight back that much, is a boss with small openings, so, heal instead and move around him.