Why does Cities: Skylines II stutter when loading MOD scenes?

While managing a mega-city, I experienced several obvious stutters that completely broke the flow of the simulation. I tried reducing population simulation accuracy, which gained me 5fps but didn't stop the temperature spikes, leaving me excited but disappointed. I entered the GamePP Fan Curve Configuration, lowered the fan start threshold to 55℃, and activated fast response mode. RTSS showed frame times converged to 14-18ms, while HWMonitor tracked a 3.5-4.1GHz fluctuation and GamePP recorded a 3s fan response delay before the fix.