Games Stutter Only When I Move the Mouse Diagonally

Games become visibly stuttery whenever I move the mouse diagonally, while horizontal and vertical movement remains smooth. Frame-time monitoring shows a flat, stable graph during the stutter, so it does not appear to be a conventional FPS or frame-pacing problem.

I have already clean-installed the graphics drivers with DDU, tested the integrated graphics and RTX 3080, tried another monitor, reinstalled the AMD chipset drivers, run SFC, changed USB ports, updated the BIOS and USB drivers, refreshed the display driver, disabled fullscreen optimizations, toggled hardware-accelerated GPU scheduling, disabled overlays, and tested multiple mice and other peripherals.

A completely fresh Windows installation temporarily fixes the problem, but it returns after rebooting. System Restore does not resolve it, and preventing Windows from automatically installing drivers has not stopped it from coming back. My system uses a Ryzen 7 5800X3D, 16 GB of Crucial Ballistix 3000 MHz RAM, a Palit RTX 3080 10 GB, an MSI MAG A520M Vector WiFi motherboard, and a Corsair TX650M power supply. Any ideas what could cause this very specific diagonal-movement stutter?