Collada export breaks bones I am trying to export a Model with a armature as .dae file to load it with Assimp into my game engine. The problem now is, Blender breaks the bones. 

This is how it looks when I am exporting. 



When I then start Blender again and try to import the dae again, I get this:



In my game engine, which renders other animated.dae files perfectly fine, it looks like this:



I am not sure where the issue is but I guess it's me being too dumb to use Blender correctly.
After googeling hours and hours i found out, Blenders Collada exporter is just buggy. For everyone who wants to use Blender and Assimp together i recommend the FBX file format. Both, Blender and Assimp do support it, you can configure Blenders FBX exporter to use the correct Coordinate-System (-z forwards, y upwards) and it even supports exporting all animations on the animation-stack as individual animations.