fog forming all the time on the camera lens over one of the sensors

my phone , on the back on the camera part, it has the main camera and you can see 4 little hotels to the left and right of the camera, on the right one, the top hole that can be seen through the glass always gets like a fog on the glass and I have to clean it ,after a while it will happen over and over again. My family has 2 other moto g5 plus same model same specs and theirs do not have this issue mine does. Anyone know which sensor is this ? and why would it fog the glass?