Help troubleshoot an issue in a C# ASP.NET project.

I need someone experienced in C# async and concurrent programming to review code in ASP.NET Web Forms project. The issue is that code executes without any issues in development environment but it takes few executions to successfully complete the task in production environment. There is no error raised and task status "RunToCompletion" each time. I want someone who can review the code and point to possible causes of this behavior.