ok thank you for the clarification, at this point I have no other ideas. My point about symmetry I need to explain it better. That is, if I have understood the situation correctly. In my sketch (I apologize for the bad quality) the two flags represent a symmetry condition.
What I am saying is that if in the plane of symmetry every displacement and rotation is fixed (as I understood from your remote displacement), then the symmetry condition is not necessary, it is “implicit”. Because no stress will get beyond your fixed point, no matter what type of loads you have. But this does not answer your problem, I know. It was just a side comment. But I would delete the symmetry condition anyway.
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