Wow. I just figured it out, and I’m not sure if there’s a fix.
For anyone else who experiences this - do you happen to have a VR headset plugged in?
Every 60 seconds a SteamVR process called vrserver.exe runs and coincides with the frametime spike. It doesn’t use any RAM or CPU so I only found this out by sorting my processes by reverse alphabetical order and sure enough, every time the frametime spike occurs, vrserver.exe pops up for a brief second.
I think this might be causing issues in other games as well, just not nearly as bad as MSFS which is a full 2 second freeze for whatever reason.
I’m working on getting a video on Youtube so I can show it.