We have the same problem. It happens on some drawings only. On the view below for instance, we have relinked the keynotes repeatedly, they are ok for some time and then become unlinked again. Keynotes have not changed.  

I have had success migrating a couple of projects that were crashing using the following method: 1. Save AC26 BIMcloud project as solo AC262. Open in AC27, save as 27, close3. Reopen using ‘repair’ option4. Detach all libraries5. Upload to BIMcloud 2...

We have the same issue with roughly half of our AC26 projects. Some migrate to AC27 BIMcloud without problems, others crash.Any solutions to this yet?Tobias