The type of the source data has an effect on its usability.
If the source data is provided as V5 part with a dead surface, then there are definitely no gaps in the surface but the high number of faces makes it difficult to offset.
If the source data is read as igs-file in V5, then you get many individual surfaces.There are often gaps between these surfaces and these need to be repaired. There are often lesser problems in offset after the repairs.
The option of reading the source data via Alias and then coverting it to V5 is also being investigated.far, the igs data read in V5 is showing the best usability.