One of our customer ist using the Zetadocs Express Version 5.3.3 with Microsoft Dynamics NAV 2009 R2 RTC.
Lateley almost everyday the following (rather unspecific) error message appears when using the save and send function:
"Failed to send report. If the problem persists please contact your administrator."

After an arbitrary time (e.g. 20min sometimes longer) the System is able to save and send the report as usual without any problems.
In the Logfile, one can see, where it fails:

Detailed Problem Description / Observations:
- The error messages seem to appear for all users at the same time, so when user A wants to save and send Document 1, user B can't save and send Document 1 either
- The Save function always works, it is only the send function that seems to cause troubles
- The users wait until the factbox has been loaded completeley before they use the save and send function
- Restart of NAV or Outlook does not help
- The errors seem to appear with all kinds of reports (e.g. 204, 205.206, 405)
- Accordindg to the users, the error messages have increased since the end of April of this year
- Sometimes the exact same document can be saved and send after it could not before
As it is shown in the log, the Codeunit 9041211 seems to cause the error message

- SharePoint Server: Microsoft Windows Server 2008 R2 Standard (x64)
- SharePoint Version: Microsoft SharePoint Server 2013
- NAV Server: Microsoft Windows Server 2008 R2 Standard (x64)
- NAV Version: Microsoft Dynamics NAV 2009 R2 RTC
Client-System
- OS Version: Windows 10 (since end of 2018)
- Outlook Version: O365, 32bit (since end of 2018)
Has anyone an idea, what could be possible reasons for this error message/behaviour?
My only guess is, that the OS and Outlook versions may be too new for the zetadocs version, but it is still very strange, that it sometimes works, but sometimes does not, even when the same data (report id / order) are processed.
Any help is appreciated.
Best Regards
Eric