This is probably related to a so-called “orphan coordinate system”. The error message may come from an under-defined internal coordinate system which is no longer used. Please try the following steps to check if there is any orphan coordinate system and remove as needed:
1. Open the database in Mechanical application
2. Clear generated results
3. Run ExposeOrphanedCoordSys.js script (attached) from within the Mechanical application (Tools > Run Macro…)
4. Close Mechanical Window
5. From Workbench Schematic, double click Model to open Mechanical again
6. The orphan coordinate system object will show up under the Coordinate Systems folder in under defined state
7. Delete this coordinate system object from the tree