When using Copy / Paste between 2 computers using flow a NULL character does show up when pasting a URL on the mac. Here are the steps to produce it:

1) In Windows copy the URL (CTRL-C) of a website in any browser (Chrome / Edge).
2) Flow to the 2nd machine using Flow.
3) Open a browser (Chrome / Edge) and paste the copied link (CMD+V)
4) You will see there is a NULL character added at the end of the string copied as shown in the image attached.

This seems to only happen when going from Windows to Mac and not the other way around. Not sure if it makes a difference but have Flow configured so that I need to press CTRL and then move to the corner of the screen to move to the other machine.