COM surrogate is a “container” that runs plugins for Windows File Explorer, so that if the plugin crashes it only takes the container with it, not Windows Explorer. It used to be that a badly written thumbnail viewer could crash your Windows file views, and this is how they fixed it. If it gets “stuck” on something, you can log out and log back in again, or restart Windows, and that should clear it. I’ll double check the thumbnail tool to make sure I’m not doing something dumb and leaving files open.