Canvas Rect Transfrom width value is infinity,

Hello everyone,I got a problem when I update my project from 2018.2.12 to 2018.4.12.The hole UI position goes wrong .The canvas render mode is set to screen-space-Camera,and I was drag the main camera in it,but Canvas Rect Transfrom width value change to infinity.But when I create a new camera and drag it into the canvas ,the width value is normal. The maincamera is connected to too many things so I can not use a new camera to replace it. I just hope is there anyone who can help me. I will be very much apprecited. ,