This is a strange bug in mod_assign during a migration from Moodle 3.8.2+ to Moodle 3.8.4+
In all assignment modules in all courses is writted '0' Participant and 0 submitted , this problem is theme independent.
In student view, we see work dropped. Also, no any notification of submission is send to professor.
Thank you for your help because we have lost all students works for instance...
Some screenshots ...