[ui5-middleware-approuter] Call to local CAP service returns 401 and weird response

[jowavp]

Describe the bug
We use the ui5-middleware-approuter to test our multi-tenant CAP application.
To be able to test multiple consumers locally, we test our applications on first-consumer-dev.localhost:8080 and second-consumer-dev.localhost:8080.

When we start the app, the correct login screen appears. The app starts building up, but when a call is sent to the local srv-api destination. This returns a 401 with a weird body response.

If we open the failed request url in the browser it shows the correct response. (http://first-consumer-dev.localhost:8080/odata/v4/service/$metadata)
If we then refresh the ap (http://first-consumer-dev.localhost:8080/index.html) it is serving correct and the data is received from the local CAP service.

Expected behavior
I expect the application to start directly with no 401 responses.

Screenshots
When opening index.html there are Error message in the console:

info server:custom-middleware:ui5-middleware-approuter GET /resources/sap/ui/core/cldr/nl.json -> http://localhost:1091/resources/sap/ui/core/cldr/nl.json [200]
#2.0#2025 04 01 01:05:26:148#+02:00#ERROR#/Handler#####87ec4877-cc83-4373-94ba-5992d45a1c6b####nfaSp2IYLxycXM4G6jYXKdgrAdjOdDUi######m8xogcji#PLAIN##GET request to /odata/v4/admin/$metadata?sap-language=NL completed with status 401 Authentication required#
info server:custom-middleware:ui5-middleware-approuter GET /odata/v4/admin/$metadata?sap-language=NL -> http://localhost:1091/odata/v4/admin/$metadata?sap-language=NL [401]
#2.0#2025 04 01 01:05:26:156#+02:00#ERROR#/Handler#####2e7764e7-0562-41aa-a430-647b322d596e####oMJBN7toE5IbqrglEyPMOY2bpUbvAcUi######m8xogcju#PLAIN##HEAD request to /odata/v4/admin/ completed with status 401 Authentication required#  
info server:custom-middleware:ui5-middleware-approuter HEAD /odata/v4/admin/ -> http://localhost:1091/odata/v4/admin/ [401]
info server:custom-middleware:ui5-middleware-approuter GET /resources/sap/ui/core/themes/sap_horizon/library.css -> http://localhost:1091/resources/sap/ui/core/themes/sap_horizon/library.css [200]

when I open the call to $metadata in the browser it is a success:

When I then refresh the browser window of the initial opened application it loads successfully.

Any Idea how I can fix this issue?

kr,
Joachim