So this is a new issue I am now having. I updated Zwift this morning, and now there is a subtle stuttering in the rider animation and maybe the background as well. It happens every 10 or 20 seconds or so. I think my fps is also lower, but that is harder to check.
Before this update Zwift was running smooth on the High setting for me. I am on a Windows 10 i7 PC with 8GB memory and a Nvidia GTX 670 card.
Other than the graphics issue, everything else seems to be fine. I am going to try again tonight after updating my graphics driver and possibly re-installing Zwift.