Check if your library folder contains non-optimized (“DEBUG” build) external libraries.

DebugFlagFolder.cs

using System.Reflection;

string[] pathNames = Directory.GetFiles(@"path\to\library\folder\");

foreach (string path in pathNames)
  {
      Assembly asm = Assembly.LoadFrom(path);
      object[] attrs = asm.GetCustomAttributes(typeof(DebuggableAttribute), false);
      Console.WriteLine("{0}:{1}", asm.FullName, (attrs.Length > 0) ? "Release" : "Debug");
  }



//NOTE:  Though it is a possibility that we can emit debug symbols with optimization turned on, but this does not happen in most cases.