This was due to the fact that when checking out files from the openCARP repository on Windows, Unix-style line endings were converted to Windows-style line endings.
It is apparently necessary that files passed to the docker executable contain Unix-style line endings.
Git configuration can be modified so that Git will not perform any conversion when checking out text files. When committing text files, CRLF (Windows-style) will be converted to LF (Unix-style):
git config --global core.autocrlf input