Large Language Models (LLMs) are of great interest in vulnerability detection and repair. The effectiveness of these models hinges on the quality of the datasets used for both training and evaluation. Our investigation reveals that a number of studies featured in prominent software engineering conferences have employed datasets that are plagued by high duplication rates, questionable label accuracy, and incomplete samples. Using these datasets for experimentation will yield incorrect results that are significantly different from actual expected behavior. For example, the state-of-the-art VulRepair Model, which is reported to have 44% accuracy, on average yielded 9% accuracy when test-set duplicates were removed from its training set and 13% accuracy when training-set duplicates were removed from its test set. In an effort to tackle these data quality concerns, we have retrained models from several papers without duplicates and conducted an accuracy assessment of labels for the top ten most hazardous Common Weakness Enumerations (CWEs). Our findings indicate that 56% of the samples had incorrect labels and 44% comprised incomplete samples--only 31% were both accurate and complete. Finally, we employ transfer learning using a large deduplicated bugfix corpus to show that these models can exhibit better performance if given larger amounts of high-quality pre-training data, leading us to conclude that while previous studies have over-estimated performance due to poor dataset quality, this does not demonstrate that better performance is not possible.