I have 2 load balanced VMS and have a web site running on them.
My web site posts an error intermittently. It does not cause the web site to crash, it causes the web site to post an error page and then the user must start over.
The error is Unable to find assembly 'App_Web_****.****. The web site is looking for a file that is generated by .NET in theWindows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\****\**** directories. The App_Web_****.**** files are the ones that .NET creates at run time when it does its run-time compilation.
My azure system is a mirrored system with 2 load balanced VMs. Without exception the file the web site is looking for is, in fact, located on the other VM. You could say that the required file is on the wrong VM. This scenario can occur on either VM.