Ropalolyst Steel Path Final Phase instant heals and dodges beam

[thantounderscore]

This occurred today.  During the final phase of the Ropalolyst battle in the Steel Path, where the Ropalolyst's body is fully vulnerable, I took it down from full health to no health, hitting it a few more times just to be absolutely sure.  I then went to use the beam on it.  As soon as the beam started, it teleported away from the center and went to full health, so the beam ended up hitting nothing.  This occurred two more times - brought it down from full health to no health, again making sure it was at no health each time, then went to use the beam on it, and it teleported away when the beam was starting up, and healed itself instantly to full.  On the fourth attempt, I brought it all the way down to no health, then I looked away for a second as I wasn't near the button, and when I looked at it again, it was yet again at full health.  It then grabbed me and killed me, and then when I revived, it instantly grabbed me again and killed me again, and I was then out of revives.