Remote proctoring, or monitoring test takers through internet-based, video-recording software, has become critical for maintaining test security on high-stakes assessments. The main role of remote proctors is to make judgments about test takers' behaviors and decide whether these behaviors constitute rule violations. Variability in proctor decision making, or the degree to which humans/proctors make different decisions about the same test-taking behaviors, can be problematic for both test takers and test users (e.g., universities). In this paper, we measure variability in proctor decision making over time on a high-stakes English language proficiency test. Our results show that (1) proctors systematically differ in their decision making and (2) these differences are trait-like (i.e., ranging from lenient to strict), but (3) systematic variability in decisions can be reduced. Based on these findings, we recommend that test security providers conduct regular measurements of proctors' judgments and take actions to reduce variability in proctor decision making.