Mektul the Forgemaster Permanently Stuck Running Away Bug

I went to kill this boss, first time the lava comes, he goes in the lava does his emote/animation/attacks and things, then runs back out. Then he does it again but he disappeared into the lava, didn't come out for several minutes, lava got to the end of the chute, I tried to run through the lava to see if I can finish him off and die pretty quick without seeing the boss again.

Give it a second attempt, it bugs out again, but this time he is stuck running towards the end of the chute and gets stuck going back and forth. It seems like I can block him with my character in a way. Took a video halfway through this, didn't get the start or the other bug out but I'm assuming that he glitched out like this on my first attempt but just ran to the start of the lava pour, so I couldn't do anything to get to him lol.

https://www.youtube.com/watch?v=j42ivYEdNl8