Why does ffmpeg report wrong or missing size information when demuxing some EXRs?
ExifTool reports a "Composite" image size of 1920x1082 on failing EXRs


This was the problem. Some multilayer EXRs were made up of multiple 1920x1080 layers, but the layers were not aligned, so the final size was incorrect (as reported by ExifTool) and ffmpeg couldn't handle it.

After correcting the EXR generation, the new image sequence worked.