Design Manager crashes when loading snippets

Question

I'm having issues with the SharePoint 2013 Design Manager, so far I've - created a new content type that inherits from the Page content type - created a new page layout in the design manager, using that content type - ensured that the status have reached "Conversion successful"

When I open the page in the design manager everything still seems fine but when I try to load the snippet GUI everything breaks, I get the error "Sorry, something went wrong An unexpected error has occurred", the exception is

Application error when access /_layouts/15/ComponentHome.aspx, Error=Sequence contains no elements  
 at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)    
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.ComponentHome.OnInit(EventArgs e)    
 at System.Web.UI.Control.InitRecursive(Control namingContainer)    
 at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

This clearly has something to do with my content type since I can create new designs for the built-in content types.

My content type looks like this, it is pretty much identical to the content type Article Page

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <!-- Parent ContentType: Page (0x010100C568DB52D9D0A14D9B2FDCC96666E9F2007948130EC3DB064584E219954237AF39) -->
  <ContentType ID="0x010100C568DB52D9D0A14D9B2FDCC96666E9F2007948130EC3DB064584E219954237AF390095DBEA0C683D4CF9A13D8FB79460C86E"
               Name="Blog Page"
               Group="Herlitz Content Types"
               Description="Blog Page Content Type"
               Inherits="TRUE"
               Version="0">
    <FieldRefs>
      <!-- System fields -->
      <FieldRef ID="{3de94b06-4120-41a5-b907-88773e493458}" Name="PublishingPageImage" />
      <FieldRef ID="{f55c4d88-1f2e-4ad9-aaa8-819af4ee7ee8}" Name="PublishingPageContent" />
      <FieldRef ID="{d3429cc9-adc4-439b-84a8-5679070f84cb}" Name="ArticleByLine" />
      <FieldRef ID="{71316cea-40a0-49f3-8659-f0cefdbdbd4f}" Name="ArticleStartDate" />
      <!-- /System fields -->

      <!-- Custom fields -->
      <FieldRef ID="{3ECA34DA-3B20-41B2-9BE4-F583A0315AD5}" Name="Herlitz_Excerpt" /> <!-- Note -->
      <FieldRef ID="{B009868E-1574-4327-B1DA-488660ADE3F4}" Name="Herlitz_Categories" /> <!-- TaxonomyFieldTypeMulti -->
      <FieldRef ID="{F931C5D7-3585-4B1C-A232-83A5FF82C311}" Name="Herlitz_CommentStatus" /> <!-- Boolean -->
      <FieldRef ID="{C7689F32-7E14-40A3-BE5A-40B90E54F420}" Name="Herlitz_PingStatus" /> <!-- Boolean -->
      <FieldRef ID="{BA5BCC76-617C-4A0A-BC24-E99F175306BF}" Name="Herlitz_IsSticky" /> <!-- Boolean -->
      <!-- /Custom fields -->
    </FieldRefs>
  </ContentType>
</Elements>

Any ideas what can be wrong with the content type?

Answer 1

Issue in my case seems to occur when you create new content type based on page content type but don't add any custom columns to the content type. Once you add one additional custom column to the content type in addition to Page content type default columns issue is gone.

Answer 2

Revisiting this issue on my Dev server, I compared my custom content type (CT), based on Page, and see there are 6 additional fields in the built-in Article CT. Just adding the missing Page Image site column to my custom CT "fixes" the Snippet Manager for my custom CT, and so does adding a new custom text site column.