After upgrading from 3.2 to 3.8, everytime a teacher duplicates any activitie or resource, it doesn't work and only a popup window apears (without any information).
As far as I can see, it happens in every course.
No debug information apears while the error ocurs, but there is always a notice shoing the following line, multiple times:
Notice: Trying to access array offset on value of type null in /var/www/lib/mustache/src/Mustache/Parser.php on line 278
Thanks to all...