This issue has been analyzed together with Microsoft Support (case number SRX617101891312213ID) and they identified it to be a networking issue on the client side. So it’s neither a SharePoint Online nor a Cloud Connector issue.
We sent Fiddler traces of the failing uploads to Microsoft and they proposed a solution as follows (quote from Microsoft):
I have checked the fiddler and found that the connection is closed by uploading those files. Please try to disable TCP Chimney […] Please follow the below article to get information on how to disable TCP chimney:https://technet.microsoft.com/en-us/library/gg162682(v=ws.10).aspx
In our tests on a machine where we were able to reproduce the issue, we disabled the TCP Chimney as follows:
We also have customers that confirmed that this helps. So please try the following:
- disable global TCP Chimney. netsh int tcp set global chimney disabled
- in addition try to disable TCP Chimney for all ports netsh interface tcp delete chimneyport localport=* remoteport=*
Note: Layer2 cannot guarantee that disabling TCP Chimney has no unwanted side effects. So if you are unsure whether to disable TCP Chimney or if this doesn’t resolve the issue, please contact your Networking Specialists for further analysis.