Thanks for your valuable suggestion! I renamed the folder and now for the first time it was executing SEN2COR. For the developers, it would be extremely useful if you can find a way to cope with with the original image names - each time manually changing the image name is not the most elegant solution. Alternatively, mention it clearly in a manual.
However, because the XML kept the original name, it completed with the following warning without displaying the corrected image:
I still did not reach to a corrected image, but it seems we are getting there.