OnInstanceEnd called to early

Hi,

We are using the Revit API interface IExportContext to export a Revit scene (document) to our software. We have experienced that some objects in the scene when they are exported we first receive a call to OnInstanceStart and expect to receive faces and materials after that (OnFaceBegin a.s.o) but instead we receive a call to OnInstanceEnd directly and after that call we get the objects faces and materials. For 99% of the objects we get the calls in the correct order but for a small number of objects the calling order seem to be incorrect. Is this a known problem with Revit API?

Regards

Robert