I had this problem and made a thread about it in the past that saving in my game (even with a blank mfa and just saving a number) caused heavy micro stutter (but it is also a bit random, so it is not happeningevery single save). Like when it saved the game would halt for a split second and then continue. The solution I found was even stranger to me. If I go into Windows Security and turn the "Real-Time Protection" toggle Off and then On again the problem is solved. However it starts occuring again if I restart my computer. I only have this problem with Fusion made games, no other games I play on Steam etc cause this so even though I have found a "solution" i am a little afraid that some number of users out there will have the same issue with my game.
Do anyone know exactly why this happens and if it is possible to solve it in a better more permanent way? Also I find it so strange that I actually don't need to turn Off Real-Time Protection and keep it off, but I can turn it on again. I just need to toggle it off and on and it works (until next restart)