Loss Knows Best: Detecting Annotation Errors in Videos via Loss Trajectories

Reliable video understanding requires high-quality video datasets that can provide both precise semantic labels and temporally consistent annotations. Detecting annotation errors in densely labeled videos is challenging because errors may arise from semantic **mislabeling**, where labels disagree with visual content, or temporal **disordering**, where otherwise plausible labels violate procedural progression. Training dynamics have been used to identify mislabeled training examples primarily for static samples. We investigate checkpoint loss dynamics for **out-of-sample auditing** of temporally annotated videos. We compute **Cumulative Sample Loss (CSL)** as the mean annotation-conditioned loss of an audit frame across checkpoints trained on a *disjoint* reference set. CSL acts as a dynamic fingerprint and captures the persistent disagreement between its annotation and learned visual-temporal structure. High-CSL frames are then flagged as likely candidates for potential annotation errors, including semantic mislabeling or temporal disordering. Experiments on EgoPER and Cholec80 show that CSL substantially outperforms final-checkpoint loss and achieves up to a **4.2-point AUC improvement** over prior baselines on EgoPER and **92.0/78.5 AUC** for mislabeling/disordering on Cholec80. These results demonstrate checkpoint loss dynamics as an effective diagnostic for temporal annotation auditing.