Cars at some distance in front of you not showing (loosing) their wheels in night race on ultra car details. with all other car detail settings everything is fine, only with ultra settings.
if car in front reaches some distance the wheels just dissapear
people have posted about this issue before many times but nothing has ever happened
maybe try submitting a ticket at the support site
https://support.forzamotorsport.net/
this thread probably should have been in the support section anyway