To reproduce:
Start MITK, activate MovieMaker, load 4D dataset.
Select either spatial or temporal as playing options. Select any window a by clicking on it.
Select combined as playing options. Select any other window b by clicking on it.
Move the slider left and right.

Expected behaviour:
Moving through timesteps while simultaneously moving through window b (2D slidewise, 3D rotating).

Actual behaviour:
Moving through timesteps while simultaneously moving through window a (2D slidewise, 3D rotating).