How to extend RDS based Gateway service which includes custom fields?

Hello all!

I'm trying to extend the GW-Service PLMI_CHANGE_RECORD_MANAGEMENT with another RDS.

Requirement: add the custom field "Project" to the "Manage Change Records" app. The field must provide a value help. A number of further custom fields need to be added, some of them with a code list.

Approach:

1. I added the custom fields as per requirement, with the Custom Fields app. This worked without problems.
2. As described by Andre Fischer in his blog post, I am trying to redefine the original service and extend it, to include the RDS (CDS) which will provide the value help for the Project field.

Problem:

I'm getting errors directly after redefining the original service. The problems seem to come (among others) from the custom fields I included in step 1 with the Custom Fields app. These seem to be specifically the fields with a code list. I have zero idea what the errors in the Function Imports are about...

The entities for the custom fields have no attributes. I guess that they are needed to provide the value help with the code list defined while creating the custom fields.

Any ideas how I can solve this issue?

Kind regards,

Szilamer