There was a typo in my code, and just copying the stream to the new call request worked as expected.

Thanks for your comment!

Ah.. That was it.

I was switching to root while building the image for installing jdk.. Adding 'USER irisowner' at the end of Dockerfile solved the issue. Thank you!

Thanks. I thought that was relevant, but even with the directory and files owned by 51773.52773, it failed with the same error.

It fails even without mounting a volume outside the container and no durable %SYS, so I was wondering if the image itself had the problem.