When course Group Mode is set to Separate or Visible, adding/removing students into/from a course group also changes the displayed group filter in the next Assignment (whose Group Mode is also set to Separate or Visible) from "All Participants" to the name of previously altered group membership.
This consistently occurs when both the Group Mode at the course level is set to either Separate or Visible groups and when the assignment level Group Mode is set to Separate or Visible (with no default grouping selected):
I've had many complaints this year off and on that when teachers go to grade something, a "random group" is selected in the Assignment's visible groups dropdown .
I can consistently replicate this behavior by placing a student into a course group or removing a student from a course group using the . Which ever group I just placed the student into or removed them from, then the very next Assignment I visit in that class will display that same group in the Separate/Visible Groups dropdown instead of All Participants.
I know the Separate/Visible groups filter will remember the last group you filtered to in the gradebook or in another assignment, but I am wondering if it's a bug that it also remembers the last group you placed a student into when visiting an assignment.
A teacher who didn't select a "default grouping" in the assignment settings would expect "All Participants" to always be shown by default when visiting an assignment. Altering a student's group membership wouldn't mean the next step for the teacher is to grade that same group in the next assignment they are opening. A teacher would treat these two actions separately.