Without knowing your setup or software installed, I recommend a complete wipe and re-install of windows then only put drivers, games, cosmos and the following on and try it.
.NET Core 3.1 Desktop Runtime x86
Link.NET Core 3.1 Desktop Runtime x64
Link.NET Core Current Runtime x86
Link.NET Core Current Runtime x64
Link.NET Framework (get latest)
LinkIf OK then keep adding the rest of the software you had on one by one and keep trying cosmos after each to see if the stutter returns.