Site microfeed throws Object reference not set to an instance of an object error

Question

I'm having issue with in a customer's SharePoint 2013 environment (CU level December'15) where sitefeed webpart throws "Object reference not set to an instance of an object" error.

When searching from ULS there are couple related errors

Microsoft.Office.Server.Social.SPSocialFeedManager.GetFeed: System.NullReferenceException: Object reference not set to an instance of an object.    
 at Microsoft.Office.Server.Social.SPSocialThread.<ProcessCrossDomainImages>b__7(SPSocialPost reply)    
 at System.Array.ForEach[T](T[] array, Action`1 action)    
 at Microsoft.Office.Server.Social.SPSocialThread.ProcessCrossDomainImages()    
 at System.Array.ForEach[T](T[] array, Action`1 action)    
 at Microsoft.Office.Server.Social.SPSocialFeed.Microsoft.Office.Server.Social.ISocialOperationResult.PostProcess()    
 at Microsoft.Office.Server.Social.SPSocialFeedManager.<>c__DisplayClass4b`1.<S2SInvoke>b__4a()    
 at Microsoft.Office.Server.Social.SPSocialUtil.InvokeWithExceptionTranslation[T](ISocialOperationManager target, String name, Func`1 func)    
 at Microsoft.Office.Server.Social.SPSocialFeedManager.<>c__DisplayClass48'1.<S2SInvoke>b__47()    
 at Microsoft.Office.Server.Social.SPSocialUtil.InvokeWithExceptionTranslation[T](ISocialOperationManager target, String name, Func`1 func)

And

SPSocialFeedManager.GetFeed: Exception: System.NullReferenceException: Object reference not set to an instance of an object.    
 at Microsoft.Office.Server.Social.SPSocialThread.<ProcessCrossDomainImages>b__7(SPSocialPost reply)    
 at System.Array.ForEach[T](T[] array, Action`1 action)    
 at Microsoft.Office.Server.Social.SPSocialThread.ProcessCrossDomainImages()    
 at System.Array.ForEach[T](T[] array, Action`1 action)    
 at Microsoft.Office.Server.Social.SPSocialFeed.Microsoft.Office.Server.Social.ISocialOperationResult.PostProcess()    
 at Microsoft.Office.Server.Social.SPSocialFeedManager.<>c__DisplayClass4b`1.<S2SInvoke>b__4a()

My assumption would be that there is some post which causes the problem but I've been unable to identify which post it might be. Tried removing the latest post in feed but that did not solve the issue. The mention of CrossDomainImages would for part suggest that issue would be with images from other domain but the SharePoint environment is closed to internal network and there should not be links to other domains. When looking the latest posts there doesn't seem to be any out of ordinary domains.

The issue affects the site in question but also rendering the whole newsfeed unusable for the newsfeed for all the users following this site.

Otherwise the newsfeed works fine so it is not due Distributed Cache or User Profile Service issues.

Any ideas?

Answer 1

We did not find the root cause of the issue in detail but after removing one discussion thread the site feed started to work again. So there was some invalid content or something else which was incorrectly referenced somewhere.

This may or may not be linked somehow to another issue which we've had longer in the system where linked documents are lost from the newsfeed as in the discussion there was lost document link and user had reposted the document as reply to the thread. -> https://sharepoint.stackexchange.com/questions/174263/document-attachment-link-not-saved-in-site-microfeed