Hi,
I don't know how to explain this issue, but I've found an issue working with an assembly save as Step.
Viewer was able to open, display and apply material on the foile without any troubles, Even the export of the file in GLB was successful. But the issue comes at the opening the file in any 3D viewer like MS 3D Viewer, or Sandbox Babylon JS, of Babylon Viewer embeded in OneDrive/Sharepoint...
I've found that the issue was in the name of the parts of the assembly.
for any reason there was either "Ø" or "," in the name of the part.
Viewer don't take care, but in the GLB I guess that it's not valid and corrupt the file.
I don't know if it is possible to "Sb" to aname when exnalyze this and correct the names of objects in the scene in respect of the syntax of the export Format.