This bug is from a mixup between (course module) id and instance id.

This is related with these bugs, perhaps:

MDL-12555 Course Module ID Incorrect on Advanced Search ...
MDL-6701 "Course Module ID incorrect" error on any ...

[STEPS]
From a teacher's profile, go to:

Activity Reports > All Logs

On this creen, click any "View Assignment Submissions".
It opens a popup window, but will say "Course Module ID was incorrect." (See screenshot.)
https://[server]/mod/assignment/submissions.php?id=9999

There is a "continue" button, but it brings the user to the course home screen, in the popup window.

[OBSERVATION]
The cause is because "id" passed to the page is that of a "course module instance id", but the page treats it as a "course module id".

This is the captured sql statement run on the page, which returns nothing (therefore causing the message).

SELECT cm.*, m.name, md.name as modname FROM mdl_course_modules cm,
mdl_modules md, mdl_assignment m WHERE cm.id = 9999 AND cm.instance =
m.id AND md.id = cm.module ;

The sql should be changed to this:

SELECT cm.*, m.name, md.name as modname FROM mdl_course_modules
cm, mdl_modules md, mdl_assignment m WHERE m.id = 9999 AND cm.instance =
m.id AND md.id = cm.module ;

But, the problem is that the sql is from
get_coursemodule_from_id
which is defined in
lib/datalib.php

=============
return get_record_sql("SELECT cm.*, m.name, md.name as modname
FROM {$CFG->prefix}course_modules cm,
{$CFG->prefix}modules md,
{$CFG->prefix}$modulename m
WHERE $courseselect
cm.id = ".intval($cmid)." AND
cm.instance = m.id AND
md.name = '$modulename' AND
md.id = cm.module");