Updating FBX without destoying animators?

I use Blender and import my FBX's. When I import them in Unity, it just duplicates the file and everything has to be reassigned, so I've been doing it outside of unity and just replacing the original FBX, as not to destroy the meta file. This was working fine, until I realized that my animations weren't correct when I did this.

The interpolation for some reason was completely broken. I know it's Unity doing it, because when I reimport the FBX into blender, everything is fine, and when i import the FBX into Unity without just replacing the original FBX outside of Unity, the animations are correct, but all of the references are broken and have to be reassigned, as it's just a duplicate of the original.

So what is the proper way to import FBX without breaking animator assignments?