User report:

We have just identified another small problem in the update, relating to group functionality administrators / editing teachers.

If only one group exists in the course, the administrator does not get a drop-down to select either ‘All participants’ or the group that exists. Instead it defaults to ‘All participants’ and does not allow this to be changed (unless the administrator has previously selected the group from within another activity in the same Moodle course, such as a forum – in that case, it defaults to the group and does not allow selection of ‘All participants’). So this would mean that in a course with just one group, the students would enter the classroom for that group, but an editing teacher would enter the ‘All participants’ room and not be able to get to the group room that the students were in!

If there is more than one group in the course, then the behaviour is as expected – the drop-down menu appears and offers the alternatives of ‘All participants’ or any of the groups.

I have used a workaround for now, by creating an additional empty group in a course which only had one group in it.