Telerik Editor Bug: Error while executing filter XHTML

So over the past couple of months I've had several of my Sitecore content writers come to me with a strange error message within Sitecore's HTML Editor (Telerik). The error is: "Error while executing filter XHTML TypeError: Unable to get property 'parentNode' of undefined or null reference". Both times it involved writers copying content from one item into another. However I could never reproduce the problem. After seeing the error show up again, I decided to investigate the issue further.

How to reproduce:
  • Open Telerik Editor
  • Switch to HTML mode
  • Paste in "<p><ul><li></li></ul></p>" (no quotes)
  • Switch back to Design mode 
  • Try to do anything (switch modes, accept, reject)

How to fix
  • Download the latest Telerik files (Telerik.Web.UI.dll, Telerik.Web.UI.Skins.dll and RichText Commands.js )
  • Backup your existing dlls and javascript
  • Deploy the latest version of dlls to /bin within Sitecore solution
  • Deploy the updated RichTextCommands.js to /sitecore/shell/Controls/Rich Text Editor/
  • Update web.config 
What's in the zip file:
  • Updated DLLs for version 2015.2.826.45 of Telerik
  • Updated RichText Commands.js as Telerik's  RadEditorCommandList is no longer supported. Must use Telerik.Web.UI.Editor.CommandList for loading custom commands.

            <assemblyIdentity name="Telerik.Web.UI" publicKeyToken="121fae78165ba3d4" culture="neutral" />
            <bindingRedirect oldVersion="2012.2.607.35" newVersion="2015.2.826.45" />
             <assemblyIdentity name="Telerik.Web.UI.Skins"          publicKeyToken="121fae78165ba3d4" culture="neutral" />
             <bindingRedirect oldVersion="2012.2.607.35" newVersion="2015.2.826.45" />

Please NOTE: Sitecore does not support this version of Telerik. This is an unofficial upgrade. Use with caution.