Measurement uncertainty is a key concept in undergraduate physics laboratory courses. Prior work has introduced two paradigms of student thinking about sources of measurement uncertainty: pointlike thinkers, who believe that a single measurement can produce the true value in an experiment, and setlike thinkers, who believe that a set of measurements is necessary to draw conclusions. Other work, however, has suggested that very few students are pointlike thinkers and many students do not apply consistent pointlike or setlike thinking in all contexts. In this work, we propose new categories to describe a complementary aspect of student reasoning related to sources of uncertainty. We administered a survey to students at 12 universities asking them to list sources of uncertainty present in four experimental scenarios. Using cluster analysis, we identify distinct patterns of student reasoning about sources of uncertainty, which provide new perspectives on student thinking about measurement uncertainty beyond the point and set paradigms. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-2139899 and National Science Foundation Grants No. DUE-1808945 and No. DUE-1809178.