I had a similar bug, in Ropalolyst steel path.
The fight was normal until the final phase.
We got Ropa's health to 0 for the final time, but when we try to do the final beam, it dodges as if it hadn't staggered.
Alad plays his voice line for shooting the beam too early, and now Ropa's health is full again, but also grey as if it was invincible.
It is not invincible, we get it's health to 0 again, same deal.
We quit, tried again, got the exact same bug.
Some other things to mention is Ropa did seem to grab us right around when we activated the beam, and also it seemed to drift towards the front of the platform when it would grab us, to the point it fell off while we were grabbed. This did not fix anything.
Also as we were quitting that first time, I noticed the synovia respawned, even though we had definitely already done those phases of the fight and they remained destroyed before host migration.
