Is there a defect in the body of the nikon d750 which, when changing lenses, does not autofocus?

There was another similar question and one of the respondents commented and had his camera case replaced. I have the same problem with my new Nikon, bought in January. Nikon wants me to send the body and lenses for it to be "examined". I can not afford to do without the camera while they're messing around. Is there not an idea on how to fix the problem, faster and without losing the camera?