It's also worth noting that as soon as copy mode is disabled ( esc+esc ) the messages pop up in the output nc.
I'm assuming the output has a buffer limit because I ran into the issue where some, but not all buffered output from the program made it to the output nc listener (not this example, but how I got into this mess ).
Or perhaps what makes more sense is that the program I'm using has a limit on how many functions it will handle at once - given that it is a single thread just async, with >1000 of these it could simply hit a limit of saying "no" and waiting for the process.stdout / process.stderr to complete before moving on.
Rob