Strange Baking-behavior - Baked texture messed up (Cylces)

Hello :),

(Cylces) iam using Blender since a longer time now and thought i understood most of its’ features but my actual bake-behavior prooved me wrong obviously … The problem is, that baking a texture seems to flip certain faces which messes up the baked version of the texture:

I created a cube, marked every seam and unwrapped it with a little padding along the edges. Then i created a simple material with a texture, diffuse and output-node. Then i painted something onto that texture using Blender’s texture paint. After that i wanted to bake this diffuse texture to a new one. Therefore i created a new texture and added a new image-texture node in the material of my cube. i selected the new (bake-)texture in that image-texture node, selected this node and baked the diffuse, color information (not the direct or indirect light) to the new (bake-)texture - just the default way to bake stuff in cycles …
But for my surprise the result was wrong. The texture information for some faces just flipped (or just rotated - don’t know exactly). Watch this picture:


See the one red dot in the corner of one of the faces? If i put the baked texture onto the cube the one red dot does not appear in the top left corner but instead in the bottom right corner which is definitly wrong.
Well so far … My first question is why does this happen and how can i fix it?

Then on top of it i recognized another strange thing: If i export that cube as fbx or obj and reimport it (export and import with default settings) and put the same material on the reimported cube and bake everything the same way, it works perfectly … so i assume that the export/import does something to the UVs which let me finally bake the correct texture … So obviously the second question is: Why does this fix the problem with the baking and what does the export/import process to the mesh?

I actually feel like an idiot since i created so many texture and suddenly cannot explain this strange behavior … Hopefully one of you can explain that.

I also did a short video where i explained and illustrated that behavior so you can better understand the problem and see it in real:

Thanks guys!

Edit: I added the according blend-file so you can test it yourself:
Deleteme.blend (659 KB)

I fixed it by myself and found the reason: If i smooth it (e.g. using auto-smooth for this object with degree 1° or edge split modifier) it bakes perfectly. I have a few other objects that behave the same way and that can be fixed with that solution. So first of all iam happy there is a solution but i would be happier if i could understand the reason for this behavior. Would be very happy if someone can explain that … Thanks …