KeyCloak Mixed Configuration Issue with AWS ECS and ALB

Question

I am struggeling with a "smalL" problem during my ECS configuration.

I have the following Infrastructure

ECS Fargate (Serverless)

1. Service which deploys 2 container (Application and KeyCloak)
2. ALB with SSL enabled.

When I open keyclauk.domain.de I am able to access keycloak. (I have attached an AWS Cert) When I try to access keycloak internally from application container to keycloak container I get an Error Message (Mixed Content: The page at 'url' was loaded over HTTPS, but requested an insecure resource 'url/auth'. This request has been blocked; the content must be served over HTTPS.)

I already configured Service Discovery and trying to communicate through this own dns zone task.service which seems to work but still get this issue.

Does anyone similar problems or advices?

Thanks!