Drag & Drop Randomly Stops Working for certain users

I started to experience this issue a few weeks ago where SharePoint Online doc libraries won't allow me to drag and drop an email message or Word doc attachment from Outlook to our Doc library. 

When we try to drag/drop the cursor changes to the 'No' symbol: 

What is perplexing about this is that it is not a permissions issue, as I can usually open the same link in Chrome and it will allow the drag/drop.  And then with no intervening actions by me, it will resolve and allow me to drag/drop in Edge a day later. 

This is now happening to another user, but it is impacting both Edge and Chrome for her.  We've tried clearing the cache to no avail.  She reports that if she saves the files to a folder on her desktop, she is able to drag/drop from the desktop folder to Edge just fine, we just cannot drag directly from Outlook to Edge randomly.