Authentication error while using SaaS Routes for custom domain in multitenancy

[#1]

Hello Experts,

@martinfrick 

I have followed this guide to incorporate custom domains and routes for multitenant CAP application:

https://github.com/SAP-samples/btp-cap-multitenant-saas/blob/main/docu/4-expert/-CloudFoundry-/custo...

I have faced issue during performing step 6 (specifically 6.14) 

While accessing application with custom route and custom domain im facing OAuth error, it looks like application tries to access xsuaa service with Saas route name (test1234) as subscriber tenant name
https://test1234.authentication.eu10.hana.ondemand.com/oauth_error

When accessing same application on same subaccount without custom SaaS route (but still with custom domain), everything works properly.

What can be reason for such issue ? oauth-redirect uris and tenant_host_pattern are populated according to guide linked above.

Thanks!