Symptom: In an assembly, when converting a part to a local part, some parameters are not converted.

Probable cause: If the parameter is created by an operation, such as an expression or a surface parameter, this operation must be in the analysis stage, because only operations in the analysis stage are copied to the local part's parameters.

Solution: From the Entities or Operations tree, right-click the parameter name and select Others > Change Stage... command:

then choose the Analysis stage and validate the dialog: