When LLMs are queried with pairwise prompts to determine causal direction between variable pairs, the aggregated edge orientations frequently contain cycles, making the causal order undefined. This failure is severe on larger graphs: GPT-3.5-turbo produces >>3k cycles on the 20-node child dataset and >>5k on the 22-node neuropathic dataset. GPT-4, despite being more capable, still produces >>10k cycles on child, >>10k on neuropathic, 684 on alzheimers, and 15 on covid-19. The paper shows that even upgrading from GPT-3.5-turbo to GPT-4 does not eliminate this failure mode.