This happened to us today as well -- yesterday evening, we ran some geoprocessing tools and then tried to create a Map Package (.mpkx). Pro crashed in the middle of this process.
Our .aprx is stored in cloud storage -- Google Drive -- which may have been "full". We tried Save As and duplicating the Map View and neither process worked.
Esri -- would you still like us to submit our faulty .aprx or are you sufficiently aware of the problem(s)?
We are able to quickly recover/rebuild this Map View so we're glad it was this particular one that was lost as opposed to one of the others. More and more, it seems like working on Esri GIS projects using cloud storage may not be feasible for us. Over the last several months, we have been having a lot of issues associated with the syncing that have caused geodatabases to just stop working. We're able to recover most of the data but not all of it. For now, we're going to implement a system by which we are working on local drives and using a sync software to sync our data with the Google Drive. Hopefully this will reduce the time-sinks that these issues can become.