I'm experimenting with Umbraco 12 and have had this problem come up a couple of times now. Last time I just reinstalled from scratch as I was only experimenting to get familiar with Umbraco 12.

I have a Document Type named "HomePage". As soon as I make any change to this Document Type U12 stops working and refuses to display and page with this Document Type, other pages with different Document Types work just fine.

Any idea how to resolve this? I've restarted IIS and no change. Other than creating a couple of Document Types and very simple templates and adding a couple of content pages, it's a completely empty fresh installation of U12.

Full log generated is:

Umbraco.Cms.Web.Common.ModelBinders.ModelBindingException: Cannot bind source content type Umbraco.Cms.Web.Common.PublishedModels.HomePage to model type Umbraco.Cms.Web.Common.PublishedModels.HomePage. Both view and content models are in memory generated, with different versions. The application is in an unstable state and should be restarted. at Umbraco.Cms.Web.Common.ModelBinders.ContentModelBinder.ThrowModelBindingException(Boolean sourceContent, Boolean modelContent, Type sourceType, Type modelType) at Umbraco.Cms.Web.Common.ModelBinders.ContentModelBinder.BindModel(ModelBindingContext bindingContext, Object source, Type modelType) at Umbraco.Cms.Web.Common.Views.UmbracoViewPage1.BindViewData(ContentModelBinder contentModelBinder, ViewDataDictionary viewData) at Umbraco.Cms.Web.Common.Views.UmbracoViewPage1.set_ViewContext(ViewContext value) at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context) at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, Boolean invokeViewStarts) at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context) at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable1 statusCode) at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable1 statusCode) at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ActionContext actionContext, IView view, ViewDataDictionary viewData, ITempDataDictionary tempData, String contentType, Nullable1 statusCode) at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor.ExecuteAsync(ActionContext context, ViewResult result) at Microsoft.AspNetCore.Mvc.ViewResult.ExecuteResultAsync(ActionContext context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters() --- End of stack trace from previous location --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync() --- End of stack trace from previous location --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope) at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger) at Umbraco.Cms.Web.Common.Middleware.BasicAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass6_1.<<UseMiddlewareInterface>b__1>d.MoveNext() --- End of stack trace from previous location --- at Umbraco.Cms.Web.BackOffice.Middleware.BackOfficeExternalLoginProviderErrorMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass6_1.<<UseMiddlewareInterface>b__1>d.MoveNext() --- End of stack trace from previous location --- at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context) at StackExchange.Profiling.MiniProfilerMiddleware.Invoke(HttpContext context) in C:\projects\dotnet\src\MiniProfiler.AspNetCore\MiniProfilerMiddleware.cs:line 114 at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass6_1.<<UseMiddlewareInterface>b__1>d.MoveNext() --- End of stack trace from previous location --- at Umbraco.Cms.Web.Common.Middleware.PreviewAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass6_1.<<UseMiddlewareInterface>b__1>d.MoveNext() --- End of stack trace from previous location --- at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestLoggingMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass6_1.<<UseMiddlewareInterface>b__1>d.MoveNext() --- End of stack trace from previous location --- at SixLabors.ImageSharp.Web.Middleware.ImageSharpMiddleware.Invoke(HttpContext httpContext, Boolean retry) at Microsoft.AspNetCore.Server.IIS.Core.IISHttpContextOfT1.ProcessRequestAsync()