SIrus FPS Drop

Since 3.11, I have the potential to have an FPS of 0 periodically when I fight Sirus.
If FPS goes to 0 and the screen stalls for a long time, I will be killed by Sirus.
It has never happened anywhere else except the Eye of the Storm.
If Vsync is set to Enable, the occurrence will be suppressed for some reason.
The cause is unknown and a fundamental solution has not been reached. Does anyone know a solution?