Component Insertion Origin Doesn't Match Family Origin

I've had this scenario come up under all sorts of different circumstances: upon insertion of a family component, the element's origin in the project doesn't seem to match up with the origin in the family. Not too long ago I had a user that was tracing a grid line to draw a beam, but the beam would always end up positioned 2" above the grid. Most recently I had this come up with a slab edge that kept inserting as offset from the slab, so I'll use that element type as an example.

Let's say you have a simple floor, and you add a slab edge to it. Upon placement, the slab edge always appears slightly offset from the floor:

 

With a slab edge, you'll want to check to make sure there is no Vertical or Horizontal Profile Offset applied:

 

Then check to make sure that the profile is drawn against the origin planes inside the family:

 

So there is no offset applied, and the profile is drawn against the family's origin planes. So why it the edge offset when placed in a project? If everything checks out for these steps, it might be that the family has been shifted from its internal origin.

To check, start by creating a new family and drawing a line extending from the origin.

 

Select the line, go to Modify | Lines > Clipboard > Copy to Clipboard.
Then go back your profile family, and go to Modify > Paste > Aligned to Current View.

 

Here you can see the origin of my reference planes has been shifted 1" to the right. Now I can select everything and move it over 1" to bring it back to its internal origin. When I delete that line and reload the family, the slab edge appears as expected:

 

As I mentioned at the beginning, this can happen with any sort of family. So if your elements seem unexplicably shifted, make sure the family origin planes weren't accidentally moved. You might want to get in the habit of pinning these just to play it safe.