Right, I created a similar model in Abaqus (rectangular shell subjected to bending but due to gravity to avoid issues with differences in surface/load definitions in Abaqus and CalculiX). I defined two identical steps with op=new (Abaqus uses op=mod by default) and the results were the same for both steps. Then I solved the same input file with CalculiX and there was a difference in results, similar to what we saw here.
I can report this problem on the CalculiX forum.
I get this error when Fixed is defined for rotations:
*ERROR in bounadd: parameter FIXED cannot
be used for rotations