The page for adding/editing multiple choice questions has a help button at the end of the heading pointing to [...]/help.php?module=qtype_multichoice&file=multichoice.html&forcelang= which is not a valid Moodle URL. All other questions type have this button pointing to [...]/help.php?module=quiz&file=[XYZ].html&forcelang=
Steps to reproduce:
1. On the course page click "Questions" in the Administration menu.
2. Select "Multiple choice" from the "Create new question" combo box.
3. Click the help button at the end of the heading "Adding a Multiple Choice question".