Answer:
These zero values are caused by the superposition type in the combination criterion: if you analyze several load cases or combinations in one result combination and define the load cases as "Variable", zero is shown for the maximum or minimum value at locations with the same signs. When using the variable ("potential") superposition, it can also happen that no load case or combination becomes effective. Zero is less than the smallest maximum value or greater than the greatest minimum value.
One solution would be to define the load cases or combinations contained in the result combination as "Permanent"; for example: RC1 = CO1/Permanent or CO2/Permanent or CO3/Permanent or CO4/Permanent.
The load cases or combinations are then compared as permanently acting. In this way, you obtain non-zero extreme values even for areas with the same sign.
