Hello. Maybe it's not a bug, but I'm not doing something right when exporting. When I export the project to the FBX format, the bones change their size. So the test project looks like in the Blender (.blend)
http://i99.fastpic.ru/big/2018/0212/e8/b9330b4e1970ae6d23252b8a95ec40e8.png
And so it looks like after export
http://i103.fastpic.ru/big/2018/0212/e4/d2685b644f66d9c621ba9304cf07c3e4.png