Please report bugs at the project github page
Before reporting an issue, please do the following in order to provide sufficient information:
In FreeCAD, go to Edit | Preferences | Output window
and tick all five
tick boxes on that panel (Record log messages, Record warnings, Record error messages, Redirect internal Python errors, Redirect internal Python output), and click OK.
Then, click View | Panels and tick Report View as well as Python Console.
Now re-create the error and copy any output and error messages which appear on either the report view or the python console. A screenshot is fine if all the relevant output is shown.
In addition, please go to Help | About FreeCAD and click "Copy to Clipboard" and paste this information into your message.
Of course, we'll be grateful if you are able to fix the bug yourself and issue a pull request at https://github.com/jaheyns/CfdOF