Symptom:In an assembly, when editing in place a part, the editing context is not associative.

Cause: To be able to use an associative editing context, the part document must meet two conditions:

• The part document must be synchronized with the assembly (which is the default case for an in-place part or a derived part for modification).
• There must be no transformation operation in the part document (commands of the Construction > Transformation menu). This is a technical constraint to maintain consistency between the state of the part in its document and in the assembly at the same time.

Special case of mirrored parts:
 When repeating by symmetry a part in the assembly, a mirrored part is created.
The mirrored document is a derivation of the source part document combined with a mirror transformation operation.

 A mirrored part of an in place part therefore does not meet the second condition, and an associative editing context cannot be used.

Solution: If the part contains a transformation operation and it is not possible to do without it, one solution is to derive the part in question for modification.