Why does my frame rate drop from 60 to 45 FPS in group combat on the Intel Core i9 13900K?

Group combat caused a sudden FPS drop to 45, a huge bottleneck. I tried increasing the page file, but it made things worse, dropping FPS to 55. I used GamePP BIOS Load-Line Voltage Adjustment Wizard to tighten timings from 16-16-16-39 to 15-15-15-38 and raise voltage to 1.25V. MemTest86 confirmed zero errors, with memory temps at 46-52℃ and VRM at 58-63℃ per AIDA64.