Same problem here. I’m in career mode. It happened to me after I flew and set up cameras with the 737 in free flight mode. Now I restarted the simulator and deselected the 737 in free flight mode, returning to the C172. I went back to career mode and now it allowed me to configure and save the cameras again, behaving correctly. There must be some conflict between the plane selected in free flight mode and the plane in career mode, interfering with the camera settings.