I was grading a group assignment. Students were allowed to work on this assignment without being in a group. However, I came to find out that my comments for those solo students were not saved. My "solution" was to put those students in their individual solo groups. That created its own problem - Canvas does not allow 1-person groups! So I had to set the group sizes to 2, which made manual group assignment very painful for a large class... 

Is this a known bug that would be fixed in the future?