Office Online Server November 2017 Errors

Office Online Server was refreshed as a new release available from MSDN or the Volume License Center in November 2017. After installing the new binary, a couple of errors may occur. I’ve reproduced this on multiple farms.

The first, and correctable error is with the RtcWatchdog.exe service. You may see similar errors to this in the Application Event Log as well as ULS log.

This is due to the binary, Microsoft.AspNet.SignalR.Client.dll looking for the binary Newtonsoft.Json.dll. The DLL is provisioned in the GAC, however it isn’t the version that the SignalR.Client.dll expects. SignalR is looking for version of the binary while the version is installed by the November 2017 OOS installer. The fix for this is simple, we perform a binary redirect. In the file “C:\Program Files\Microsoft Office Web Apps\Rtc2Watchdog\Rtc2Watchdog.exe.config”, add the following lines before the closing </configuration> element.

You do not need to restart any services after making this change.

The second error is with UlsFileWriterWatchdog.exe. This particular error I do not believe is correctable without a patch from Microsoft, but what you’ll see in the ULS logs is similar to this:

Neither of these appear to have an end-user impact, but they will flood the ULS as well as Application Event Logs every few seconds.


  1. I’ve done a fresh install of OOS 2016 (November 2017 update) on Windows Server 2016 and installed the OOS update (KB4011020) and created a new farm, configured Exchange 2016 for WACDiscoveryEndpoint and can browse the website fine to see the XML output but despite all this the edit option still does not show in OWA for attachments?

    I have edited the Rtc2Watchdog.exe.config as per this post which helped with the one error reoccurring in the event log but I have hundreds still for UlsFileWriterWatchdog.exe and Get-OfficeWebAppsMachine is still showing as Unhealthy so what am I doing wrong and why can’t I see the edit option on attachments?

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