New Measure adding occures unexpected error

Yes, I'm having similar issues with this new version of the Desktop - both 32- and 64-bit versions.  First, I added table descriptions in the Power Query interface.  Then, I noticed that all my tables that were connected to external data sources (mostly MS Access) had been set to "No Load" (names italicized).  I set them all back to "Enable Load" and "Refresh" and then attempted a mass refresh.  Within Power Query, the refresh worked and all previews were updated.  Then upon "Close and Apply", I got a message that it failed because a needed table was deleted.  Problem was that the table was NOT deleted and I could interface with it within the Report builder.  I reported it and started re-doing things with a copy of the original file.

Once the table descriptons were updated in the new file, I began cleaning up my measures and adding comments to them.  After doing about 25 or so (and intermittently saving), the application just stopped working and said to close it.  After doing so, the file will reload, tables will appear, the data model is there, but there are no report pages.  I've got like 30 pages that have just disappeared.  Tried opening the file in a 64-bit version and the same thing - data, model, relationships, but no report pages.

Any idea how I get my pages back?  Looks like, in addition to very frequent saves, we've now got to also do frequent backups.

PS did not get any error message to display; just said "...stopped working" and Debug or Close.