port changes back to 19132 regardless of set values

If I change the port in the docker compose file and in server.properties, it gets changed back to 19132 when the server starts. Is this by design? My ISP has 19132 locked so I need to use a different one.

Start by tracing the container startup handling for the Docker Compose port and server.properties values. Reproduce the issue with a non-default port, then verify that the configured port is preserved after the server starts and that the relevant tests or startup checks pass.

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