Students moving into the dorms in the fall may be matched as roommates by interest surveys, or mutual request.
Students moving into the dorms in the spring get whatever is available, often effectively random. The spaces available may be, on average, with roommates more likely to have roommate compatibility issues, since some of the students moved out or changed rooms due to roommate issues. So it would not be surprising if students moving into the dorms in the spring are more likely to have more roommate issues than those moving into the dorms in the fall.