Twixtor Pro V7.2.0 -

Change the Image Prep tool to Contrast/Edge Enhance to help the plugin better distinguish edges.

If still warping, your original footage might be too low FPS (e.g., 24fps) to slow down significantly. Twixtor Pro v7.2.0

Enable delinearize in the Twixtor settings to handle brightness changes properly. Change the Image Prep tool to Contrast/Edge Enhance