CPU Load Problem during use of Mask Editor

I am using MATLAB 2016a on a Windows 7 environment.

Normally CPU Load is not a problem especially without running a simulation. But when I work inside a Simulink model, open the mask editor and try to add an parameter and the new parameter is highlighted than without doing any other action the cpu load is increasing dramatically from nearly 0% cpu load to over 50 % cpu load. If I deselect the new parameter in the Parameter tab e.g. that I go back to Initialization tab, cpu load return to nearly 0%.

The effect is unpleasant because working with mask editor will reduce the load capacity of my machine to serve other applications.

How can this be? What can I do?