That's not an error. It's a warning. Does anything go wrong actually? Or do you just want to get rid of the warning?
To get rid of the warning, isolate your script from the GUI configuration:
See https://winscp.net/eng/docs/scripting#configuration
Though as you have non-default transfer settings configured in the GUI, make sure your script does not rely on those.

Seems to be a straightforward put command, but the scripting errors.

Moving a text file. Can't figure out why I am getting an error. I can move it manually.