Exporting structure as STL damages the model

I was attempting to design a 3d-printed truss structure (to print and load-test) , but the edges somehow fail to join. The edge showing tool shows naked edges in the model , but none of the tools that are meant to join/fix edges work and fail.
Attempting to CreateSolid also fails (removes most of the surfaces)

The problem is , when I export this file as a .STL and open it in my slicer (Simplify3D) the joint edges of the truss structure are removed (not completely , but the beams are not connected) and the structure is basically a group of beams mid-air.
Another unexpected issue is that some random surfaces appear once the model is sliced , but there are no such surfaces in the .STL or the Rhino model.

I attempted to remove the beams which were causing the naked edge but that did not fix my problem. (and there are still a couple of naked edges available)

edge issue without some beams:
(there are no naked edges in this part of the structure which led me to believe it has nothing to do with naked edges)

edge issue with the beams and unexpected surface appearing which is not a part of my design nor a software-added element:

Hello - probably best to Mesh the object, inspect the mesh in Rhino and then export the mesh.


Also check to see that you are not way far from the origin and that the file tolerances you have set are reasonable for the model size/scale. If you still can’t manage, post the model here.

Hello and thanks !
creating a mesh did not change the situation. I also decreased the tolerance (from 0.001 to 0.0001 cm and angles from 1 to 0.1)
I do not exactly understand the “far from origin” situation but I do not believe that is the case with my model.
I also tried grouping , removing non-essential parts such as leftover points and increasing and refining the mesh , but the gaps between the beams are persistent and don’t change (even slightly)

this is my model , Id be grateful if anyone would take a look:
loadtest_truss_3dp.3dm (2.4 MB)

thanks in advance

Hello - your model is made up of multiple parts, some of which are not closed - ideally this would be one closed solid object - that is, all the tubes trimmed to one another and joined.