Microsoft updates causing issues.

It's Friday morning and nothing makes Friday more interesting than a production issue and your manager calls up :).

A month back my team member started to troubleshoot a problem with XPS pages saved to database showing up as blank at customer places and interesting thing is that not everyone were having this issue and in our environment not all servers are having either. So the programmer started to analyze, break down the steps in understanding where exactly the root cause is while looking into the code to see if code has changed or any assemblies have changed causing the problem. Mind you, this code was huge and took quite an effort to break them into steps during the process, write test application to see if we can recreate the scenario with the same code, looking at environment differences. After breaking our heads all this while and heading no-where, we turned our attention to Microsoft updates that happened on servers which are working versus non working ones. Alas, we figured out that the culprit indeed was a MS update KB 4040973 which was installed on non -working servers.

Fix for this issue resolution was to update with patch KB 4043764

https://support.microsoft.com/en-us/help/4043764/quality-rollup-for-net-framework-4-6-4-6-1-4-6-2-and-4-7-for-windows-7

So in future if i come across such interesting and weird issues, i now know to look for MS updates as well as one of the troubleshooting steps.

Happy troubleshooting :).