Generated Models missing PublishedElementModel on generated model.

[martinmcd1]

I am currently using
umbraco v 8.9.0
modelsbuilder 8.1.6
modelsbuilder.api 8.1.6

When I run "Build Models" using the .mb file some of my generated models are missing base classes. So for example i get the following which is missing the PublishedElementModel class.

//------------------------------------------------------------------------------
//
// This code was generated by a tool.
//
// Umbraco.ModelsBuilder v8.1.6
//
// Changes to this file will be lost if the code is regenerated.
//
//------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Web;
using Umbraco.Core.Models;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Web;
using Umbraco.ModelsBuilder;
using Umbraco.ModelsBuilder.Umbraco;

namespace Umbraco.Web.PublishedModels
{
///

Accordion

[PublishedModel("accordion")]
public partial class Accordion
{
// helpers
#pragma warning disable 0109 // new is redundant
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
public new const string ModelTypeAlias = "accordion";
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
public new const PublishedItemType ModelItemType = PublishedItemType.Content;
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
public new static IPublishedContentType GetModelContentType()
=> PublishedModelUtility.GetModelContentType(ModelItemType, ModelTypeAlias);
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
public static IPublishedPropertyType GetModelPropertyType(Expression<Func<Accordion, TValue>> selector)
=> PublishedModelUtility.GetModelPropertyType(GetModelContentType(), selector);
#pragma warning restore 0109

	// ctor
	public Accordion(IPublishedElement content)
		: base(content)
	{ }

	// properties

	///<summary>
	/// Anchor name
	///</summary>
	[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
	[ImplementPropertyType("anchorName")]
	public string AnchorName => this.Value<string>("anchorName");

	///<summary>
	/// Background colour
	///</summary>
	[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
	[ImplementPropertyType("backgroundColour")]
	public Umbraco.Core.PropertyEditors.ValueConverters.ColorPickerValueConverter.PickedColor BackgroundColour => this.Value<Umbraco.Core.PropertyEditors.ValueConverters.ColorPickerValueConverter.PickedColor>("backgroundColour");

	///<summary>
	/// Disable block
	///</summary>
	[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
	[ImplementPropertyType("disableBlock")]
	public bool DisableBlock => this.Value<bool>("disableBlock");

	///<summary>
	/// Text
	///</summary>
	[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
	[ImplementPropertyType("text")]
	public string Text => this.Value<string>("text");

	///<summary>
	/// Title
	///</summary>
	[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder", "8.1.6")]
	[ImplementPropertyType("title")]
	public string Title => this.Value<string>("title");
}

}

I tried changing the modelsbuilder mode to Dlls and it successfully generates the class inheriting the PublishedElementModel.

Any ideas?
Thanks,
Martin