Why does frame drop repeatedly in desert? Is VRAM exceeding limit?

Frame time spiked to 45ms as VRAM hit 7.8GB during desert traversal. I tried lowering textures to Medium, but RTSS still showed 20-35ms instability. I used GamePP Resource Scheduler to set background priority to Normal and game to High. Subsequently, GamePP monitoring confirmed VRAM dropped to 6.2GB, and RTSS recorded stable frame times of 12-15ms, eliminating the stutter.