Subsidence, or the sinking of land, threatens the U.S. Gulf Coast, where millions face growing flood risks from sea-level rise. Measuring the subsidence is essential for coastal planning and climate adaptation. Satellite radar (InSAR) is widely used to measure subsidence, but studies often disagree. Comparing two recent datasets, we found widespread disagreements except in dense urban areas. Decision makers should use coastal InSAR products with caution until these discrepancies are resolved.