Hello,

We faced a major issue on updating production machine. Even thou all changes been reverted still getting following error:

Cannot bind source type Umbraco.Web.Models.RenderModel to model type GMCS.WebUI.Models.BaseRenderModel.

or

Umbraco.Web.Mvc.ModelBindingException: Cannot bind source type Umbraco.Web.Models.RenderModel to model type GMCS.WebUI.Models.ProductModel.

etc.

Where BaseRenderModel is(quite simple):

public class BaseRenderModel : RenderModel
    {
        private readonly IPublishedContent _content;
        private CultureInfo _cultureInfo;

        public BaseRenderModel(IPublishedContent content, CultureInfo culture) : base(content, culture)
        {
            _content = content;
            _cultureInfo = culture;
        }

        public BaseRenderModel(IPublishedContent content) : base(content)
        {
            _content = content;
        }

        public BaseRenderModel() : this(new UmbracoHelper(UmbracoContext.Current).TypedContent(UmbracoContext.Current.PageId))
        {

        }
    }

This error occurs for every page that uses either base model or models inherited from base model.

As I mentioned above, update files were reverted but error persisted. No configuration files were modified.

One of the problems, that we don't have access to machine beside FTP access to application root.

So far I found 2 solutions to this problem:

1. Clean up .NET temp fodler (works in approximate 50% of attempts, tested on staging machine while getting same issue.)
2. Copy of application folder and change IIS app path. (this method works 100% of the time, but looks too barbarian and taking in account that no access to production machine, it makes things even more complicated.)

I saw that this bug was discovered upon migration to version 7.4.2. After reading corresponding materials I still don't have real answer why that happens and how to avoid such situations.

Umbraco version used - 7.5.2

Thank you in any advice.