I've observed the same issue, also playing on a 55" TV. I've tried both 1080p and 4K, using a GeForce nVidia GTX 1080 Ti. Maybe it has something to do with using HDMI. For now I've taken to using a controller, but the mouse and keyboard controls are more flexible, so I'd prefer them if possible. However, the tiny cursor makes it significantly harder to play--I keep losing track of it.