An asset can look correct in its source application and still fail after import into A-Frame. Treat import diagnostics as a translation problem between tools, with importer warnings and missing or changed data checked on both sides.
For A-Frame, reproduce the import once with logging enabled, then isolate the first feature that changes or disappears. Compare importer warnings before and after import instead of changing several exporter settings at once.
Capture the first importer warning, reduce the file to the smallest failing case, and change one export option at a time. Apply this import diagnostics guidance to the actual A-Frame delivery path.