Alright. I baked the animation and I made sure that Unroll Rotations is selected. Then I opened the Graph Editor while selecting all baked bones, I selected all keyframes and applied the Euler Filter. That's it.
Nope. Even the Euler Filter won't work. Is the euler filter supposed to fix the huge difference between values in some parts of the animation? (for example: a value of -140 turns into a value of 1050 in the next frame)