Thanks! I needed that. What I found in today's Architect log was
UIWnd::ElementQuery() failed, code: 262158
Thread: 1548 Load resource by hash 2870995805 failed
Loading resource "/common/Fonts/Calibri.ttf" by hash 2870995805 failed
UpdateServiceResponse parser: tag is missed.
Fail to query OnlineServiceAPI service object: corresponding service is not supported by the service provider.
Corresponding ribbon item not found by selector: [plugin-convert-required]
UIDocumentFramePanelsManager CheckPanelsDimensions incorrect geometry!
I haven't looked at the other log files.
At Julian's suggestion, I turned off the Hibernate feature. But I deleted the offending file; I downloaded the original file, performed the conversion, and all went well this time.