warning: the VM is running with native name encoding of latin1 which may cause Elixir to malfunction as it expects utf8. Please ensure your locale is set to UTF-8 (which can be verified by running "locale" in your shell)
I had a similar issue, which was caused by setting the locale in the wrong stage in a multi stage build. If you have a multi stage build, make sure you are setting the locale in the final container that the release gets copied into.