Shader/lighting bug all of a sudden

Hello!

I’ve downloaded a unity asset package from the asset store with some trees and other foliage in it (made by the Unity team and free). I loved it and used it and everything looked awesome, untill one of my trees just stopped working properly.
Normally it looked allright and as it should, but all of a sudden, it looks like this (se pic below) and I have NO clue how to fix it. I’ve been trying to look through options but I haven’t found anything that works.

Help is very much appreciated!

I’ve figured out why the problem occur.

It’s when you change the “scale factor” preference on the model in unitys project list. Once you’ve used that scale factor, the shadows and lights get all messed up and it stays that way even if you try to undo the previous action.
Still don’t know how to revert the effect though.

Only way I can fix this problem is if I delete the entire asset and reimport it. This doesn’t work for my fellow group mates however, they keep getting the bugged tree no matter how many times they delete the entire asset (model, materials, textures etc) and reimport them with our SVN server.

Does anybody know why this is happening?

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