Rotation along one axis does not work Sorry if this question already exists, but I didn't find the answer to my problem.

(BLENDER v2.78)

I recently had the idea to animate a toon-style Rubik's Cube. I used Blender Render. I added 26 Cubes to the scene and added assigned simple materials for each color.
For scrambling it I selected manually the 9 cubes I wanted to move, rotated them and set the keyframe. Everything worked perfectly and I got this result:

h*ttps://i.stack.imgur.com/JyJcb.png (I can only post 2 links)

Then I wanted to animate a whole solving process with the same file.
I deleted all the keyframes and scrambled the cube with selecting all the 9 cubes of one side and pressing e.g. R + X.

After scrambeling I've set the keyframes just the same way like I did during scrambeling and got this result just in the middle of the scrambled postion and the "1st move keyframe" (Only one 90 degrees rotation along the global x-axis after scrambeling it):



I regarded the Location of the strange tiles and saw that also the y and z coordinated have been modified.

Can someone please help me.
I don't know what happened and how I can fix it.

The File: 

Rubiks Cube.blend
As binweg found in another post, the problem has been the Euler Rotation.
I changed the rotation of every cube to Quaternion and everything worked as it was meant to be.