Halation is a reddish glow around high contrast edges caused by light passing through all the layers of film, but the brightest areas bouncing off the back of the film or camera body and into the lower layers of emulsion.
Halation is common with 800T, especially in backlist scenes or with bright lights facing the camera.
If you don't want halation, you can avoid it by shooting in more evenly lit scenes.
This effect is common with Cinestill 800T - some people love it, some don't - we don't mind it in certain scenes but try to avoid it when taking portraits. You can avoid halation by shooting in even / more controlled light. This effect is most common with bright overexposed highlights that directly face the camera.