RichText box error: undefined: Cannot read properties of undefined (reading 'getvalue')

I’ve created a very simple customization that simply attempts to populate a richtext box on a button click.  The box renders as a white area without the richtext box header, which I’m fine with.

I’m getting a “undefined: Cannot read properties of undefined (reading 'getvalue')” message as a popup.  Others have had this in the past (question from two years ago is the same).  I’ve tried the suggested solution without success.

Here is my current ASPX code for the control...

      <pxa:PXRichTextEdit AllowImageEditor="False" AllowInsertParameter="False" AllowLinkEditor="False" AllowNull="True" Required="False" ID="CstPXTextEdit5" runat="server" 
            Style="z-index: 113; border-width: 0px;"
            AllowAttached="true" AllowSearch="true" AllowLoadTemplate="false" AllowSourceMode="true"
            DataField="Answer" Width="800" Height="900">
            <ContentStyle BorderStyle="None" ></ContentStyle>
            <AutoSize Enabled="True" ></AutoSize>
        </pxa:PXRichTextEdit>

I have a zipped customization that shows the error…