Exception: ReflectionTypeLoadException on sewitch web

If I switch build type to web this error occurs

 Internal compiler error. See the console log for more information. output was:
 Unhandled Exception: System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.
   at (wrapper managed-to-native) System.Reflection.Assembly:GetTypes (bool)
   at System.Reflection.Assembly.GetTypes () [0x00000] in <filename unknown>:0 
   at Mono.CSharp.RootNamespace.ComputeNamespaces (System.Reflection.Assembly assembly, System.Type extensionType) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.RootNamespace.ComputeNamespace (Mono.CSharp.CompilerContext ctx, System.Type extensionType) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.GlobalRootNamespace.ComputeNamespaces (Mono.CSharp.CompilerContext ctx) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Driver.LoadReferences () [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Driver.Compile () [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Driver.Main (System.String[] args) [0x00000] in <filename unknown>:0 

Any suggestion on how to debug this? I have deleted all assembled code and the library.

Edit: Problem was a 3rd party asset using reflection an unsorted call in webplayer.