Why does the game stutter severely when saving large city files?

Managing this medieval manor requires careful save frequency because every save triggers severe system frame drops. I first tried increasing the page file size in Windows; while available memory increased, the write stutters remained, proving it was a hardware issue. I used GamePP NVMe Queue Depth Configuration to limit write concurrency to 32 and enabled smart cache management. CrystalDiskMark showed write speeds stabilized to 400-800MB/s, HWInfo confirmed temps at 40-48℃, and SLC drops were 1500 to 120 MB/s.