Symptom: When editing an in-place part, the assembly environment is displayed in transparency or wireframe depending on the context.
For some unknown reason, some parts may remain in wireframe rendering when leaving in-place editing to return to the assembly.
In this case, some parts have the wireframe rendering attribute enabled without the user having intentionally changed it.

Solution: The most practical solution to get back to a normal display is the following one:

• Activate the display of all the parts of your assembly,
• Make an enclosing box of all parts in the graphics area,
• Right-click and run the Attributes... contextual command,

• Uncheck the Wireframe rendering option and validate,