Unable to reproduce internally, but appears related to users storing their projects in shared cloud storage folders. All Error Messages seem to indicate projects in Drive or Dropbox folders.
Update by Eric.K: "after a little more digging into each reported version of this crash. It appears this has something to do with Dropbox, Google Drive or OneDrive syncing the project directory and some file is not correctly allowed to update in the Intermediate Folder while compiling a Material or other element. I am attempting to reach out to someone who had this issue and get a project that I can try to sync to a dropbox and reproduce."
I reproduced crashes by using ShaderWorkingDir= to remap the source temp files to the destination drive, and then filled up all the space.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-20945 in the post.