There are two tools available for fixing GUIDs. For instructions how to run tools please click here.
This tool scans the model and finds all invalid and duplicate GUIDs. The IFC GUID has a exact format that specifies how long the GUID must be and which characters are allowed. If the tool finds invalid or duplicate GUIDs it creates new GUIDs for those objects.
This tool re-creates the GUIDs for all objects. The GUIDs created by this tool are unique also in a case insensitive comparison. GUID comparisons should be case sensitive, but there are some applications that use case insensitive comparison, and those applications can have problems with perfectly valid IFC models where GUIDs differ only by case.
Use this tool only if you for some reason need to re-create all GUIDs or if you encounter the rare condition described above.