CQN subquery not working for local/external services in CAP

[Tobi-NR]

Hello everyone,
I'm currently developing a CAP (Node.js) app with an Fiori Elements Analytical List Page.
The data for the Analytical List Page should come from an OData V4 RAP service on S/4.
To load the data from the remote service into the Analytical List Report, a CQN subquery is generated and supplied to the CAP service handler as follows:

const extSrv = await cds.connect.to("RAP_SERVICE");

this.on("READ", ENTITY, async (req) => {
  return await extSrv.run(req.query);
});

The query looks like in the attached CXN query (i.e., it is a subquery):
Exemplary_CXN_Query.json

According to the Capire documentation you can use a query as source in the "from" property : https://cap.cloud.sap/docs/cds/cqn#from

This works but only when you run the query using cds.run(query). My requirement is to execute the query in other services i.e., srv.run(). But when i try doing that it gives the following error:

[cds] - TypeError: Cannot read properties of undefined (reading 'map')

This error occurs also when running the app locally.

A similar discussion was already started here, but yet unanswered: https://community.sap.com/t5/technology-q-a/cqn-subquery-not-working-for-local-external-services-in-cap/qaq-p/14010868

So my questions would be: Is this a bug in the CAP framework? Do you know and workaround for that issue?

Many thanks!
Best regards,
Tobias