Insert your view engine at correct position

The exception was:

[InvalidOperationException: The model item passed into the dictionary is of type 'X', but this dictionary requires a model item of type 'Y'.]

Turned out we have a view in a folder named Search in our project and that view was selected by our custom view engine when doing a Shell search. Shell search is routed to /UIUrl/cms/Search/.

The solution? Either rename the controller and folder to something else or make sure our engine is inserted after EPiServer.Shell.Web.Mvc.ModuleViewEngineCollection. For obvious reasons, I went for the second option.