I have the same problem at my organization. We're using ESET Endpoint Antivirus (version 6.2.2033.1) and ESET Remote Administrator Agent (version 6.2.190.0) running on Windows 7 and Windows 10 based PCs. Most of Windows 7 machines run Office 2013, several have Office 2016 (365), while all Windows 10 machines have Office 2016 (365) installed.
I've found common factor for every computer that had this issue - its Office 2016 has been updated to version 1801. I have several computers with Office 2016 1612 (updates were disabled for that PC) and Office 2016 1708 (delayed upgrades branch) and these do not have this issue. I personally contacted every person that notified us about this issue and every single one of them had O2016 1801 installed on their PCs.
Dear ESET staff, please try running ESET Outlook Add-in with Office 2016 1801, this should replicate the issue.
Best regards
