Hi again Wilfried
Being reminded again of the existence of Windows-based Moodle servers, I just checked the state of a fix I rolled out on 1 Jan 2018 that affected the python2, python3, octave-function and java-method question types on Windows-based Moodles. I discover that I actually re-introduced the bug on 27 January. So if I'm right that you're using a Windows-based Moodle, and you're using one of those 4 question types, I'm afraid you'll need to go through the process described in the last two postings of the thread entitled "Issues with the Check button" to fix the prototypes. Sorry about that. I really will fix it properly next time :)
Richard