The imported Civil CAD files are the strongest causal indicator. Imported CAD data becomes embedded within the Revit model rather than remaining externally referenced. Civil drawings frequently contain large coordinate extents, dense linework, hatches, proxy objects, unnecessary layers, and complex geometry. Embedding several such files can substantially increase model size, graphical processing requirements, opening time, and synchronization duration.

The audit specifically establishes that no significant native Revit geometry was added, eliminating option A as the principal explanation. Revit model backups are normally maintained externally or through version history rather than being accumulated as embedded model data in the manner suggested by option B. An increase from 600 to 750 warnings warrants review, and certain warning types can affect regeneration performance, but that increase alone is less likely to explain a doubled file size and a sudden 40% synchronization penalty.

The appropriate corrective action is to assess whether the CAD files can be linked instead of imported, clean them before use, remove unnecessary layers and objects, verify their coordinates, and purge obsolete imported definitions after removal.

Reference topics: Revit model health; imported versus linked CAD files; file-size management; performance auditing; model warnings; civil-background coordination.

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