Bug: Curve features are converted to densified line segments from an arc in a SQL Server geodatabase after compression
Beginning with ArcGIS 10.5, feature classes that are created in a geodatabase in SQL Server and use Geometry or Geography storage store attributes such as pointIDs, multipatches, and parametric entities (true curves) directly in the business table. Prior to ArcGIS 10.5, this information was stored in a side table that joined with the business table.
When compressing versioned edits in the delta tables into the base tables, additional geometric elements stored in the GDB_GEOMATTR_DATA column do not move.
Feature classes created in an ArcGIS 10.5 or 10.5.1 geodatabase using a 10.5 or 10.5.1 client use a new storage model for geometry attributes, which stores them in a new column (GDB_GEOMATTR_DATA). If a geodatabase has been upgraded from an older release to ArcGIS 10.5 or 10.5.1, the feature classes still use the old model where these geometry attributes are stored in a side table unless the feature class is migrated to the new model using the Migrate Storage geoprocessing tool.
When a feature class using the new model is registered as versioned, the adds (A###) table also has the new column for storing geometry attributes.
If versioned edits occur that insert data into the new column, those geometry attribute values are not pushed to the base table during compress. For example, if a circular arc is inserted while performing versioned edits, the edit is saved into the adds table. The densified curve is stored in the SHAPE column, and the geometry attribute information about the true curve is stored in the GDB_GEOMATTR_DATA column. When the geodatabase is compressed, the row is pushed into the base table, but the data stored in the GDB_GEOMATTR_DATA column is lost. As a result, the compressed feature is now only a densified arc rather than a true curve.
This behavior is addressed in the next release of ArcGIS. If using ArcGIS 10.5 or 10.5.1, please apply the ArcGIS (Desktop, Engine, Server) SQL Server Compress Patch associated with the release to all ArcGIS clients that access the geodatabase.
Advanced editing tools and parcel fabric data workflows are highly susceptible to this issue. Edits should not be compressed unless the ArcGIS client has been patched.