we have been working on trying to troubleshoot and solve this problem for about a month now.
Some of our users, not all (each running Windows 10 and what should be the latest version of Office 2016) receive an Upload Failed notice when trying to edit and save documents they checked out from our instance SharePoint Online
The IT staff has been unable to replicate the problem with their own accounts, the problem is not happening for every user using the files, and the problems don't always occur for those who are having the problems. It has been very hard to troubleshoot.
We have tried working with the Upload Center & tried clearing the Office document Cache directory. Sometimes it seems like it works, other times it seems like it deletes the files that we thought uploaded successfully but unfortunately still facing same issue.
We do have good number of people working on the documents,

