It'll have something to do with the rotation of the blades. You need to be able to mix in all areas of the bowl. Try it with just the hand mixer, I bet it will work!
I couldn't afford a fancy stand mixer like Kitchen Aid or Kenwood, over here they are £250 + so I bought this one
It was only £110... quite a saving, and it works like a dream!
The difference between your mixer and my mixer is that the blade spins whilst going in a circle motion
Your spins whilst stationary, and as you turn the bowl it is still stationary, you don't get the movement around the bowl.
Correct me if I'm wrong, just want to help you experience IMBC