Lesson check_updates callback is failing when the activity uses separated groups

Create a new empty course forced to use separate groups Create two groups in the course: g1 and g2 Now, enrol a user as teacher Enrol two users in the course (u1 and u2) as students, add the u1 to the group g1 and the u2 to the group g2 Create a lesson in the course with just one question page (any type of question except essay) Take the lesson with u1 and u2 As admin, enable "Mobile services": Site administration ► Mobile app ► Mobile settings Create a Token in the mobile app service for the teacher user in the course: Click on Site administration ► Plugins ► Web services ► Manage tokens Next, you can do a CURL REST call simulating a WS client with the user. You need to replace the wstoken, the course id, the since with a timestamp value from a day ago and the URL of your moodle instance curl 'http://localhost/m/stable_master/webservice/rest/server.php?moodlewsrestformat=json' --data 'courseid=17&since=1476274596&wsfunction=core_course_get_updates_since&wstoken=a70d553bbaf6d9b260a9e5c701b3c46e' | python -m "json.tool" Confirm that you receive updates for both users in the course. For example, in usertimers you see two items. In userquestionattempts you see 2 items too. Now, unassign (prohibit) the moodle/site:accessallgroups capability in the course for the teacher role. Enrol the teacher in the group g1 Execute again the curl request and now check that you only get 1 item in usertimers or userquestionattempts (you get just one now because you can see the u1 right now)