A field report tested 49 project files saved by Revit 2024 to 2027; 25 carried an older release's element-record marker and all 25 read as zero elements and zero Levels. 8 of those markers turned out to be Revit 2022 and 2023 schemas in files whose history starts in 2014 to 2020.
From the Grok pain-radar digests, Oct 28-29 2026 (Oct 28 8:41 AM ET through Oct 29 early-morning Haitch editions). Verified live 2026-10-29: issue/PR read; title and state confirmed.