Why do frames spike during Total War Warhammer III battles?

In the heat of a massive charge, the frame generation time suddenly jumped from 11ms to 42ms per RTSS, which is fatal during tactical moves. I tried updating all drivers in Device Manager, but the stuttering remained and I even experienced occasional crashes, making me very anxious. I used the GamePP Peripheral Driver Conflict Detector to set conflicting sync services to manual and optimized I/O priority. Frame intervals converged to 9-13ms per RTSS, and CPU temperature stayed at 72-78℃ per AIDA64.