(Solved)Final boss fight stuck at 1% health

[LuckyEstheim]

Currently on the final boss fight. I can whittle down the emperor really quickly all the way to the phase where he starts doing a mass summoning of his minions, which is apparently supposed to be his last phase. However, as soon as he becomes vulnerable after this, his health is stuck at 1% and can't be finished off for some reason. Have tried resetting checkpoints and letting myself die to reset the fight but no luck so far.
EDIT: Apparently returning to the main menu and loading my save up was the fix needed for it! I'll leave this up in case anyone else runs into a similar/identical issue.

[Taketori]

My experience with the final boss was awful. Performance had gotten increasingly shoddy throughout the game, but this boss was such a choppy mess with lower than expected GPU utilisation, massive framedrops and stuttering. My system should be able to handle this game, but it brough my 3070 to its knees.