First check the permanent magnet, it is a black ring that the the armature fits into, if it is cracked and chipped you are screwed. If not the camera and gimbal is just a press fit, make sure where to armature is going into the housing is clean and make sure your ribbon cable isn't damaged or it will need to be replaced. Press them together as they are a press fit and check that there is no wobble or play in the gimbal unit as sometime the hole the shaft goes through gets wobbled out. If so use the red locktite or if you can get it their green super strong industrial stuff. Now when you power it up the camera may not be aligned right or it just sits and hunts for the right position. Then you need to adjust the alignment of the shaft. It is easy to do the phantom 2 vision + is similar.
I know this is the Inspire 1 thread but many of us have had other phantom and if we can help, what harm does it do.