Import existing fbx from blender to Unity destroys prefab

Hey guys, I have a prefab based on a fbx. Several days of work redoing it, dont want to!

I need to change something in the fbx because of errors in the model found late in development. I import the fbx into blender. And then just export right away. Now the pivopoints for all objects not using orgin as pivo is screwed over. So the prefab looks like a Picasso painting. Mind you I have not messed aroudn with the objects inside the fbx yet. Just omport / export, boom. Whats going on?

Example
One of the objects positions in old file


And here after import/export in Blender


Since the pivo is competly change the prefab will become a mess.
How can I remedy this?

 

if it really is several days of work to rebuild a prefab, it might be worth spending the money on this
https://www.assetstore.unity3d.com/en/#!/content/70665

 

I did it in 4 hours, so no biggie. Used the old prefab as template, verticesnapped the new model to the old and could move everything over and keep localpos that way. Also now I have a .blender file I can use for future updates to the .fbx. But it would have been nice to know why it changed the pivopoints