Von Misese Stress looks spotted

Hello folks,

I have a problem with the evaluation of the von mises stress of a simulation. The display of the stress looks spotted. Are there similar experiences with simulating a force parallel to a temperarture load? I used different mesh sizes but the problem still remains.

The force of 50 N is applied to the inner face of the part (see the atteched). The temperature is applied to all faces.

What could be the problem?

Best regards

SolidworksSimulation