Troubleshooting models

Intro
This page is to help find solutions to problems that can occur across multiple modeling commands. Errors specific to a certain command should be put on the appropriate wiki page for the command.

Troubleshooting FAQ
Part Turns Black
 * Cause: Faces that should be on inside are on outside
 * Resolution: Try creating part using commands in a different order

Part Design Command will not complete with Not Contiguous Solid error
 * Cause: Part Design commands only work with continuous body
 * Solution: Create sepereate body if there should be space between bodies or check that sketches are at least flush with existing body.

FreeCAD crashes while creating fillets or chamfers
 * Cause: OCC bug that causes a crash when an invalid fillet or chamfer is attempted
 * Solution: Change radius to valid value

My edge based features keep changing position
 * Cause: Topological naming is not stable meaning edge and face names change, changing which face etc. you feature is based on.
 * Solution: Finish the main design work of your solid body before applying features like fillets and chamfers.

My face based features keep changing position
 * Cause: Topological naming is not stable meaning face names change, changing which face your feature is based on.
 * Solution: Do not use the attach to face feature for defining sketchs. Use a datum plane instead.

Command fails to complete with TopoDS::Edge, TopoDS::Shell, BRep_API: command not done or BRep_Tool:: no parameter on edge
 * Cause: OCC call fails. The selection(s) made to define your command are incorrect or lead to a case that is not handled by OCC.
 * Solution: Try using different selections for command or using a different command.