There is a bad value in the package.json file that causes the application to print an error message at every start:

(node:8) [DEP0128] DeprecationWarning: Invalid 'main' field in '/usr/local/lib/node_modules/@alo5/availability/node_modules/node-getopt/package.json' of './lib'. Please either fix that or report it to the module author
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(Use `node --trace-deprecation ...` to show where the warning was created)

When used in a docker container, this error message is not printed on STDERR but redirected to STDOUT causing side effect when it is desired to redirect semantically relevant output to a file.