IDML files are blank

Given that the first rule of troubleshooting an InDesign file that's crashing is to save it to an IDML file, and use that, it's a little disconcerting that the last few times I've had issues exportding IDML files.  It seems to export all right, but when I open up the newly created IDML file, it has one blank page, and the document doesn't even have my settings (like it has facing pages when the document i exported doesn't).  How do you troubleshoot the most important troubleshooting technique?
Oh, and I'm on an M1 Mac running MacOS 15.5, InDesign 20.3.1, and EasyCatalog 20.0.2.