ASP.NET MVC: Exception rendering view in new thread

I want to create a process in my ASP.NET application that I trigger manually and will send a bunch of emails to my users. Since this process takes a while I am creating a new thread to send these messages and prevent having timeouts in my web app. (I know this is error prone in case the app pool is recycled or there’s an unhandled exception in the app, but that’s another subject).

ASP.NET MVC Recompilation limit of 15 reached HostingEnvironment initiated shutdown HostingEnvironment caused shutdown

At some point, shortly after a code push, we saw numerous restarts occurring in our web application with no logging indicating an issue whatsoever. So I found this article: http://weblogs.asp.net/scottgu/433194 and we added Application_End logging, which immediately revealed this: