Recently, we have applied SharePoint 2019 Cumulative January 2020 CU (KB 4493162, KB 4493161) in our SharePoint 2019 farm, the new Cumulative update is installed successfully, but I had noted that the RSS Web Part is broken although it was worked before!
An unexpected error occurred processing your request. Check the logs for details and correct the problem
I have checked the logs and I have found the RssWebPart Exception
RssWebPart: Exception handed to HandleRuntimeException.HandleException System.ArgumentNullException: Value cannot be null.
I am not sure if the RSS Web Part is broken due to the new cumulative update. but it's the last action we have did! Also, we have checked another farm that not updated yet, and the RSS web is working!
How I fix this RSS web part exception? Can I rollback the newly installed SharePoint cumulative update?