If you experience geometry issues after saving an IFC file from SimpleBIM make sure you do not remove "Original Materials".
Make sure you leave "Originals Materials" on the left side in "IFC Export Settings" as shown here:
While removing materials in itself is not a problem,
it might affect geometry depending on how IFC exporters / importers work in different BIM software.
At this time developers are looking into the issue.
So for now leave "Original Materials" on the left side.