Repair Geometry (Data Management) documentation state that SDE Geodatabases automatically check each geometry's validity during loading but invalid geometries can still be loaded.
The article below explains further this phenomena and how to deal with such occurances.FAQ: Why does the Check Geometry tool sometimes find errors in ArcSDE feature classes?<a href="http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=29465" target="_blank">http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=29465</a>