We have come across the issue with 'Intermittent AppDomain Recycling of ASP.NET applications' being caused due to the unexpected changes in Application subdirectories, config files etc.
AppDomain recycling can cause the issues like- “Loss of in-proc stored Session variables”, “assemblies will be unloaded (it will be reloaded again on the next request)” and “code can be re-compiled”. Consequently, this affects the performance of the application severely.
Most of the issues that we come across had the cause identified as the “Antivirus” which was causing the unexpected changes to the application subdirectories and config files.
I found a very useful blog written by my colleague Amol, which talks about the exclusions list for the Antivirus while you run the ASP.NET application on IIS:
Hope this helps 🙂