I suspect a faulty element in the file.
Trouble shoot by removing the Objects.
Because of calling GDL library elements, a file size when stored by ArchiCAD bears no relationship to the 3D model size. Even a tiny file can make a huge file making overbearing demands on RAM.
For example, a file with 10,000 high-polygon chairs will only be tiny, but when assembled by ArchiCAD for a 3D view, it will grow enormously because all of the imaging data must be maintained at the same time to solve the image.
Dwight Atkinson