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Machining Allowances should be applied to every functional surface. Adjacent Faces should be selected at once, to create one coherent Machining Allowancecontinuous geometry. Therefore, the automatic execution mode can be turned off.
Tip: To have an easier access to the Non-Design Spaces choose the picking Filter “Cells” and hide the Design Space Cell so that only the Non-Design Spaces are visible. Simply choose a whole Non-Design Space by drawing a rectangle like shown in the picture below.
Now your Assembly should look like this.
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