INDD Beta 19.4 filesharing bug?

My teammate and I regularly collaborate remotely using the INDD Beta App. Yesterday, he invited me to open an INDD Beta App file...it shows the initial page of the file (as always), with the first page of the document and then I click on the arrow in the upper left corner of screen to go to the shared files screen. The actual doc/file is not there (but all the other files we've worked on over the year are still there and I can still access them). He has regularly shared docs with me and I have worked inside those docs for a year without issue. Called Adobe, the tech suggested it was a bug and to share this. He also suggested the teammate save the file he's sharing as a new file with a new file name and see if that works.... I'm waiting for him to do this.  Will try to come back here and report.