Question about Scissors-like elements

I built a scissor-like bridge like this:

it can rotate in the left to simulate the construction phase. But I meet a question. When the scissors-like elements (SLEs) is inclined, the deformation of SLEs is deviant under gravity. The deformation is large when the expansion angle is small, which can be seen in the following picture.

in the picture, the scissor-like bridge is in the totally folded state and the deformation is small, which may be several mm or cm.
So, what’ wrong with my model? And the related file can be seen in the following.
施工阶段.gh (271.3 KB)