Why does FPS drop from 45 to 15 during combat in No Rest for the Wicked?

Facing a giant Boss, every time I released a large skill, the frame rate would drop from 45 to 15, which was a total nightmare. I tried increasing the virtual memory to 16GB, but while it stopped the crashes, the stuttering frequency actually increased. I then used the GamePP Resource Scheduler to set the game's memory priority to Highest and forced a cleanup of background cache. Frame generation time converged to 18-25ms per RTSS, and memory temperature stayed at 42-48℃ per HWMonitor.