Error when steps are writing final result to stdou in Close()

[alek-thunder]

If a step that writes its result to stdout during Close() is used in combination with multiple inputs, a fork and an output that writes to stdout an error occurrs. Example pipeline:

bitflow-pipeline "{wally172.cit.tu-berlin.de:8050 wally173.cit.tu-berlin.de:8050 wally174.cit.tu-berlin.de:8050} -> fork_tag(tag=vm, regex=true) { '.+' -> print_tags(tag=volumes) -> text://- }"

ERRO[Mar 30 17:10:26.653] stdout printer: Error closing output: close /dev/stdout: file already closed
ERRO[Mar 30 17:10:26.653] stdout printer: Error closing output: close /dev/stdout: file already closed
ERRO[Mar 30 17:10:26.653] stdout printer: Error closing output: close /dev/stdout: file already closed
ERRO[Mar 30 17:10:26.653] stdout printer: Error closing output: close /dev/stdout: file already closed

The reason why it occurs only in combination with the fork and multiple inputs could be due to some runtime timing issues?
I was not able to reproduce this behavior when either removing the multi-input or the fork.
However, the above example pipeline reproduces the error constantly on my machine at least.