When done modeling a part is it possible to move the part so that the parts center of mass is at the origin? Or is it possible to set up the part from the beginning so that the part origin updates as the center of mass changes (as features are added).
If you use the 3 default planes (front, right, top) for any type of mating/alignment in an assy, you will have errors. Always create the part with the origin on the mounting surface, center of the part. When you show center of mass, it will tell you how far from the origin.
If you use the front plane to create your first sketch of the part, then mate that part in an assy using the front plane (the front plane goes through the origin), the part can move or you can get mate errors if your part moves in relation to the origin. (I’m using the front plane as example)
Above is a snippet.